Breaking into computer networks from the Internet. [email protected] 2000/12/31 First run 2001/07/01 Updated a bit 2001/09/20 Added Trojans © 2000,2001 Roelof Temmingh & SensePost (Pty) Ltd - 1 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] Chapter 0: What is this document about anyway?.........................................................4 Chapter 1: Setting the stage...........................................................................................5 Permanent connection (leased line, cable, fiber).......................................................6 Dial-up.......................................................................................................................6 Mobile (GSM) dial-up...............................................................................................6 How to........................................................................................................................7 Using the 'net.............................................................................................................8 Other techniques........................................................................................................9 Chapter 2: Mapping your target...................................................................................10 Websites, MX records…DNS!................................................................................10 RIPE, ARIN, APNIC and friends............................................................................13 Routed or not?..........................................................................................................16 Traceroute & world domination...............................................................................16 Reverse DNS entries................................................................................................17 Summary..................................................................................................................18 Chapter 3: Alive & kicking ?.......................................................................................24 Unrouted nets, NAT.................................................................................................24 Ping - ICMP.............................................................................................................25 Ping -TCP (no service, wrappers, filters).................................................................26 Method1 (against stateful inspection FWs).........................................................26 Method2 (against stateless Firewalls)..................................................................29 Summary..................................................................................................................30 Before we go on.......................................................................................................30 Chapter 4 : Loading the weapons.................................................................................30 General scanners vs. custom tools...........................................................................31 The hacker's view on it (quick kill example)...........................................................31 Hacker's view (no kill at all)....................................................................................34 Chapter 5: Fire!............................................................................................................36 Telnet (23 TCP).......................................................................................................36 HTTP (80 TCP)........................................................................................................38 HTTPS (SSL2) (443 TCP).......................................................................................40 HTTPS (SSL3) (443 TCP).......................................................................................41 HTTP + Basic authentication...................................................................................43 Data mining..............................................................................................................44 Web based authentication........................................................................................45 Tricks...................................................................................................................47 ELZA & Brutus....................................................................................................48 IDS & webservers....................................................................................................48 Pudding....................................................................................................................49 Now what?...............................................................................................................50 What to execute?..................................................................................................53 SMTP (25 TCP).......................................................................................................54 FTP (21 TCP + reverse)...........................................................................................55 DNS (53 TCP,UDP).................................................................................................57 Finger (79 TCP).......................................................................................................59 NTP (123 UDP).......................................................................................................61 RPC & portmapper (111 TCP + other UDP)...........................................................61 TFTP (69 UDP)........................................................................................................63 SSH (22 TCP)..........................................................................................................64 - 2 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] POP3 (110 TCP)......................................................................................................64 SNMP (161 UDP)....................................................................................................65 Proxies (80,1080,3128,8080 TCP)...........................................................................66 X11 (6000 TCP).......................................................................................................67 R-services (rshell, rlogin) (513,514 TCP)................................................................68 NetBIOS/SMB (139 TCP).......................................................................................68 Chapter 6 : Now what?................................................................................................70 Windows..................................................................................................................70 Only port 139 open - administrator rights............................................................71 Port 21 open.........................................................................................................71 Port 80 open and can execute...............................................................................71 Port 80 and port 139 open....................................................................................74 What to execute?..................................................................................................74 Unix..........................................................................................................................76 What to execute?..................................................................................................76 Things that do not fit in anywhere - misc................................................................76 Network level attack - Source port 20,53............................................................77 HTTP-redirects....................................................................................................77 Other Topics.................................................................................................................78 Trojans (added 2001/09)..........................................................................................78 - 3 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] Chapter 0: What is this document about anyway? While I was writing this document a book "Hack Proofing Your Network" was released. I haven't been able to read it (dunno if its in print yet, and besides - everything takes a while to get to South Africa). I did however read the first chapter, as it is available to the public. In this chapter the author writes about different views on IT security - hackers, crackers, script kiddies and everything in between. I had some thoughts about this and decided that it was a good starting point for this document. I want to simplify the issue - let us forget motives at the moment, and simply look at the different characters in this play. To do this we will look at a real world analogy. Let us assume the ultimate goal is breaking into a safe (the safe is a database, a password file, confidential records or whatever). The safe is located inside of a physical building (the computer that hosts the data). The building is located inside of a town (the computer is connected to a network). There is a path/highway leading to the town and the path connects the town to other towns and/or cities. (read Internet/Intranet). The town/city is protected by a tollgate or an inspection point (the network is protected by a firewall, screening router etc.) There might be certain residents (the police) in the town looking for suspicious activity, and reporting it to the town's mayor (the police being an IDS, reporting attacks to the sysadmin). Buildings have their own protection methods, locks chains, and access doors (on-host firewalling, TCP wrappers, usernames and passwords). The analogy can be extended to very detailed levels, but this is not the idea. In this world there are the ones that specialize in building or safe cracking. They are not concerned with the tollgates, or the police. They are lock-picking experts - be that those of the house, or of the safe. They buy a similar safe, put it in their labs and spend months analyzing it. At the end of this period they write a report on this particular safe - they contact the manufacturer, and might even build a tool that can assist in the breaking of the safe. Maybe they don't even manage to crack into the safe - they might just provide ways to determine the type of metal the safe is made of - which might be interesting on its own. These people are the toolmakers, the Bugtraq 0-day report writers, the people that other hackers consider to be fellow hackers. And the rest? The rest are considered to be tool users - a.k.a. script kiddies. They are portrayed as those rushing into towns, looting and throwing bricks through windows, bricks that were built by the toolmakers mentioned in the previous paragraph. They don't have any idea of the inner workings of these tools. They are portrayed as those that ring the doorbell and then runs away, just to do it a trillion times a day - those that steals liquor from the village restaurant to sell it in their own twisted village. A scary and dangerous crowd. Is there nothing in between these groups of people? Imagine a person with a toolbox with over a thousand specialized tools in it. He knows how to use every one of these tools - what tool to use in what situation. He can make some changes to these tools - not major changes, but he can mold a tool for a specific occasion. He knows exactly where to start looking for a safe - in which town, in what building. He knows of ways to slip into the town totally undetected, with no real ID. He knows how to inspect the safe, use the correct tools, take the good stuff and be out of town before anyone detected it. He has a X-ray machine to look inside a building, yet he does not know the inner workings of the machine. He will use any means possible to get to the safe - even if it means paying bribes to the mayor and police to turn a blind eye. He has a network of friends that include tool builders, connections in "script kiddie" gangs and those that build the road to the town. He knows the fabric of the buildings, the roads, the safes and the servants inside the buildings. He is very agile and can hop from village to city to town. He has safe deposit boxes in every city and an ultra modern house at the coast. He knows ways of getting remote control surveillance - 4 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] devices into the very insides of security complexes, and yet he does not know the intricacies of the device itself. He knows the environment, he knows the principals of this world and everything that lives inside the world. He is not focused on one device/safe/building/tollgate but understands all the issues surrounding the objects. Such a person is not a toolmaker, neither is he a script kiddie, yet he is regarded as a Script Kiddie by those who calls themselves "hackers", and as such he has no real reason for existence. This document is written for the in-between group of people. Toolmakers will frown upon this document and yet it may provide you with some useful insight (even if it better the tools you manufacture). It attempts to provide a methodology for hacking. It attempt to answers to "how to" question, not the "why" or the "who". It completely sidesteps the moral issue of hacking; it also does not address the issue of hackers/crackers/black hats/gray hats/white hats. It assumes that you have been in this industry long enough to be beyond the point of worrying about it. It does not try to make any excuses for hacking - it does not try to pretend that hacking is a interesting past-time. The document is written for the serious cyber criminal. All of this sounds a bit hectic and harsh. The fact of the matter is that sysadmins, security consultants, and IT managers will find this document just as interesting as cyber criminals will. Looking at your network and IT infrastructure from a different viewpoint could give you a lot of insight into REAL security issues (this point has been made over and over and over and I really don't to spend my time explaining it again [full disclosure blah blah whadda whadda wat wat]). A note to the authors of the book "Hack proofing your network" - I truly respect the work that you have done and are doing (even though I have not read your book - I see your work every now and again). This document will go on the Internet free of charge - this document does NOT try to be a cheap imitation of what you have done, it does not in any way try to be a substitute (I am a tool user, where as you are tool writers...remember? :) ) Before we start, a few prerequisites for reading this document. Unless you want to feel a bit left in the cold you should have knowledge of the following: 1. Unix (the basics, scripting, AWK, PERL, etc.) 2. TCP/IP (routing, addressing, subnetting etc.) 3. The Internet (the services available on the 'net-e.g. DNS, FTP, HTTP, SSH, telnet etc.) 4. Experience in IT security (packetfiltering, firewalling, proxies etc.) I have written this document over a rather long period of time. Sites and tools could be outdated by the time you read this. I wrote the document with no prior knowledge about the "targets". You will find that in many cases I make assumptions that are later found not to be true. Reading through the text will thus provide you with an un-edited view of the thought processes that I had. Chances are very good that I am talking a load of bullshit at times - if you are a terminology expert, and I have used your pet word in the wrong context - I am really sorry - it won't ever happen again. Now please leave. In the case that I totally go off track on technical issues - please let me know. Also my English sucks, so if I loose track of the language please bear with me - I tried to write it in simple words. This is not an academic paper!! Chapter 1: Setting the stage. Before you can start to hack systems you need a platform to work from. This platform must be stable and not easily traceable. How does one become anonymous on the Internet? It's is not that easy. Let us look at the - 5 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] different options (BTW if this chapter does not seem relevant you might want to skip it): Permanent connection (leased line, cable, fiber) The problem with these connections is that it needs to be installed by your local Telecom at a premise where you are physically located. Most ISPs wants you to sign a contract when you install a permanent line, and ask for identification papers. So, unless you can produce false identification papers, company papers etc., and have access to a building that cannot be directly tied to your name, this is not a good idea. Dial-up Many ISPs provides "free dial-up" accounts. The problem is that logs are kept either at the ISP, or at Telecom of calls that were made. At the ISP side this is normally done using RADIUS or TACACS. The RADIUS server will record the time that you dialed in, the connection speed, the reason for disconnecting, the time that you disconnected and the userID that you used. Armed with his information the Telecom can usually provide the source number of the call (YOUR number). For the Telecom to pinpoint the source of the call they need the destination number (the number you called), the time the call was placed and the duration of the call. In many cases, the Telecom need not be involved at all, as the ISP records the source number themselves via Caller Line Identification (CLI). Let us assume that we find the DNS name "c1-pta-25.dial-up.net" in our logs and we want to trace the attacker. We also assume that the ISP does not support caller line identification, and the attacker was using a compromised account. We contact the ISP to find out what the destination number would be with a DNS name like that. The ISP provides the number - e.g. +27 12 664 5555. It's a hunting line - meaning that there is one number with many phone lines connected to it. We also tell the ISP the time and date the attack took place (from our logs files). Let us assume the attack took place 2000/8/2 at 17h17. The RADIUS server tells us what userID was used, as well as the time it was connected: (these are the typical logs) 6774138 2000-08-02 17:05:00.0 2000-08-02 17:25:00.0 demo1 icon.co.za 168.209.4.61 2 Async 196.34.158.25 52000 1248 00010 B6B 87369 617378 null 11 These logs tell us that user "demo1" was connected from 17h05 to 17h25 on the date the attack took place. It was dialing in at a speed of 52kbps, it send 87369 bytes, and received 617378 bytes. We now have the start time of the call, the destination number and the duration of the call (20 minutes). Telecom will supply us with source number as well as account details - e.g. physical location. As you can see, phoning from your house to an ISP (even using a compromised or free ID) is not making any sense. Mobile (GSM) dial-up Maybe using a GSM mobile phone will help? What can the GSM mobile service providers extract from their logs? What is logged? A lot it seems. GSM switches send raw logging information to systems that crunch the data into what is called Call Data Records (CDRs). More systems crush CDRs in SCDRs (Simple CDR). The SCDRs is sent to the various providers for billing. How does a CDR look like? Hereby an example of a broken down CDR: 99042300000123000004018927000000005216003 27834486997 9903220753571830 834544204 000001MOBILE000 0000001000000000000000000 - 6 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] AIRTIME1:24 20377 UON0000T11L MTL420121414652470 This tells us that date and time the call was placed (1st string), the source number (+27 83 448 6997), the destination number (834544204), that it was made from a mobile phone, the duration of the call (1 minute 24 seconds), the cellID (20377), the three letter code for the service provider (MTL = Mtel in this case), and the unique mobile device number (IMEI number) 420121414652470. Another database can quickly identify the location (long/lat) of the cell. This database typically looks like this: 20377 25731 -26.043059 28.011393 120 32 103 "Didata Oval uCell","Sandton" From this database we can see that the exact longitude and latitude of the cell (in this case in the middle of Sandton, Johannesburg) and the description of the cell. The call was thus placed from the Dimension Data Oval in Sandton. Other databases provide the account information for the specific source number. It is important to note that the IMEI number is also logged - using your phone to phone your mother, switching SIM cards, moving to a different location and hacking the NSA is not a good idea using the same device is not bright - the IMEI number stays the same, and links you to all other calls that you have made. Building a profile is very easy and you'll be nailed in no time. Using time advances and additional tracking cells, it is theoretically possible to track you up to a resolution of 100 meters, but as the switches only keep these logs for 24 hours, it is usually done in real time with other tracking devices - and only in extreme situations. Bottom line - even if you use a GSM mobile phone as modem device, the GSM service providers knows a lot more about you than you might suspect. How to So how do we use dial in accounts? It seems that having a compromised dial in account does not help at all, but common sense goes a long way. Suppose you used a landline, and they track you down to someone that does not even owns a computer? Or to the PABX of a business? Or to a payphone? Keeping all of above in mind - hereby a list of notes: (all kinda common sense) Landlines: 1. Tag your notebook computer, modem and croc-clips along to a DP (distribution point). These are found all around - it is not discussed in detail here as it differs from country to country. Choose a random line and phone. 2. In many cases one can walk into a large corporation with a notebook and a suit with no questions asked. Find any empty office, sit down, plug in and dial. 3. etc...use your imagination GSM: 1. Remember that the device number (IMEI) is logged (and it can be blocked). Keep this in mind! The ultimate would be to use a single device only once. - never use the device in a location that is linked to you (e.g. a microcell inside your office) - 7 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] 2. Try to use either a very densely populated cell (shopping malls) or a location where there is only one tracking cell (like close to the highway) as it makes it very hard to do spot positioning. Moving around while you are online also makes it much harder to track you down. 3. Use prepaid cards! For obvious reasons you do not want the source number to point directly to you. Prepaid cards are readily available without any form of identification. (note: some prepaid cards does not have data facilities, so find out first) 4. GSM has data limitations - currently the maximum data rate is 9600bps. Using the 'net All of this seems like a lot of trouble. Is there not an easier way of becoming anonymous on the Internet? Indeed there are many ways to skin a cat. It really depends on what type of connectivity you need. Lets assume all you want to do is sending anonymous email (I look at email specifically because many of the techniques involved can be used for other services such as HTTP, FTP etc.). How difficult could it be? For many individuals it seems that registering a fake Hotmail, Yahoo etc. account and popping a flame email to a unsuspected recipient is the way to go. Doing this could land you in a lot of trouble. Lets look at a header of email that originating from Yahoo: Return-Path: <[email protected]> Received: from web111.yahoomail.com (web111.yahoomail.com [205.180.60.81]) by wips.sensepost.com (8.9.3/1.0.0) with SMTP id MAA04124 for <[email protected]>; Sat, 15 Jul 2000 12:35:55 +0200 (SAST) (envelope-from [email protected]) Received: (qmail 636 invoked by uid 60001); 15 Jul 2000 10:37:15 -0000 Message-ID: <[email protected]> Received: from [196.34.250.7] by web111.yahoomail.com; Sat, 15 Jul 2000 03:37:15 PDT Date: Sat, 15 Jul 2000 03:37:15 -0700 (PDT) From: RH <[email protected]> Subject: Hello To: [email protected] MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii The mail header tells us that our mailserver (wips.sensepost.com) received email via SMTP from the web-enabled mailserver (web111.yahoomail.com). It also tells us that the web-enabled mailserver received the mail via HTTP (the web) from the IP number 196.34.250.7. It is thus possible to trace the email to the originator. Given the fact that we have the time the webserver received the mail (over the web) and the source IP, we can use techniques explained earlier to find the person who was sending the email. Most free web enabled email services includes the client source IP (list of free email providers at www.fepg.net). How to overcome this? There are some people that think that one should be allowed to surf the Internet totally anonymous. An example of these people is Anonymizer.com (www.anonymizer.com). Anonymizer.com allows you to enter a URL into a text box. It then proxy all connections to the specified destination. Anonymizer claims that they only keep hashes (one way encryption, cannot be reversed) of logs. According to documentation on the Anonymizer website there is no way that even they can determine your source IP. Surfing to Hotmail via Anonymizer thus change the IP address in the mail header. But beware. Many ISPs make use of technology called transparent proxy servers. These servers is normally located between the ISP's clients and their main feed to the Internet. These servers pick up on HTTP requests, change the source IP to their own IP and does the reverse upon receiving the return packet. All of this is totally transparent to the end user - therefor - 8 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] the name. And the servers keep logs. Typically the servers cannot keep logs forever, but the ISP could be backing up logs for analyses. Would I be tasked to find a person that sent mail via Hotmail and Anonymizer I would ask for the transparent proxy logs for the time the user was connected to the web-enabled mailserver, and search for connections to Anonymizer. With any luck it would be the only connections to the Anonymizer in that time frame. Although I won't be able to prove it, I would find the source IP involved. Another way of tackling the problem is anonymous remailers. These mailservers will change your source IP, your <from> field and might relay the mail with a random delay. In many cases these remailers are daisy chained together in a random pattern. The problem with remailers is that many of them do keep logs of incoming connections. Choosing the initial remailer can be become an art. Remailers usually have to provide logfiles at the request of the local government. The country of origin of the remailer is thus very important as cyberlaw differs from country to country. A good summary of remailers (complete with listings of remailers can be found at www.cs.berkeley.edu/~raph/remailer-list.html). Yet another way is to make use of servers that provide free Unix shell accounts. You can telnet directly to these servers (some provide SSH (encrypted shells) access as well). Most of the free shell providers also provide email facilities, but limit shell capabilities -e.g. you can't telnet from the free shell server to another server. In 99% of the cases connections are logged, and logs are kept in backup. A website that list most free shell providers are to be found at www.leftfoot.com/freeshells.html. Some freeshell servers provider more shell functionality than others - consult the list for detailed descriptions. How do we combine all of the above to send email anonymously? Consider this - I SSH to a freeshell server. I therefor bypass the transparent proxies, and my communication to the server is encrypted and thus invisible to people that might be sniffing my network (locally or anywhere). I use lynx (a text based web browser) to connect to an Anonymizer service. From the Anonymizer I connect to a free email service. I might also consider a remailer located somewhere in Finland. 100% safe? Even when using all of above measures I cannot be 100% sure that I cannot be traced. In most cases logs are kept of every move you make. Daisy chaining and hopping between sites and servers does make it hard to be traced, but not impossible. Other techniques 1. The cybercafe is your friend! Although cybercafes are stepping up their security measures it is still relatively easy to walk into a cybercafe without any form of identification. Sit down, and surf to hotmail.com - no one would notice as everyone else is doing exactly the same thing. Compose your email and walk out. Do not become a regular! Never visit the scene of the crime again. When indulging in other activities such as telnetting to servers or doing a full blast hack cybercafes should be avoided as your activity can raise suspicion with the administrators. 2. Search for proxy like services. Here I am referring to things like WinGate servers. WinGate server runs on a Microsoft platform and is used as a proxy server for a small network (read SOHO environment with a dial-up link). In many cases these servers are not configured correctly and will allow anyone to proxy/relay via them. These servers do not keep any logs by default. Hoping via WinGate servers is so popular that lists of active WinGates are published (www.cyberarmy.com/lists/wingate/). 3. With some experience you can hop via open routers. Finding open routers are very easy - many routers on the Internet is configured with default passwords (list of default passwords to be found at - 9 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost] www.nerdnet.com/security/index.php )Doing a host scan with port 23 (later more on this) in a "router subnet" would quickly reveal valid candidates. In most of the cases these routers are not configured to log incoming connections, and provides excellent stepping-stones to freeshell servers. You might also consider daisy chaining them together for maximum protection. 4. Change the communication medium. Connect to a X.25 pad via a XXX service. Find the DTE of a dial-out X.25 PAD. Dial back to your local service provider. Your telephone call now originates from e.g. Sweden. Confused? See the section on X.25 hacking later in the document. The exact same principle can be applied using open routers (see point 3) Some open routers listens on high ports (typically 2001,3001,X001) and drops you directly into the AT command set of a dial-out modems. Get creative. The best way to stay anonymous and untraceable on the Internet would be a creative mix of all of the above-mentioned techniques. There is no easy way to be 100% sure all of the time that you are not traceable. The nature of the "hack" should determine how many "stealth" techniques should be used. Doing a simple portscan to a university in Mexico should not dictate that you use 15 hops and 5 different mediums. Chapter 2: Mapping your target Once you have your platform in good working order, you will need to know as much as possible about your target. In this chapter we look at "passive" ways to find information about the target. The target might be a company, a organization or a government. Where do you start your attack? This first step is gaining as much as possible information about the target - without them knowing that you are focussing your sniper scope on them. All these methods involve tools, web sites and programs that are used by the normal law abiding netizen. Websites, MX records…DNS! For the purpose of this document, let us assume that we want to attack CitiBank. (no hard feelings CitiBank). We begin by looking at the very obvious - www.citibank.com. You would be amazed by the amount one can learn from an official webpage. From the website we learn that Citibank has presence in many countries. Checking that Citibank have offices in Belgium we check the address of www.citibank.be and the Malaysian office www.citibank.com.my. The IP addresses are different - which means that each country' Citibank website is hosted inside the specific country. The website lists all the countries that Citibank operate in. We take the HTML source code, and try to find the websites in each country. Having a look around leaves us with 8 distinct countries. Maybe XXX.citybank.XXX is registered in the other countries? Doing a simple "host www.citibank.XXX" (scripted with all country codes and with .com and .co sub extensions of course) reveals that following sites: www.citibank.as www.citibank.co.kr www.citibank.at www.citibank.co.nz www.citibank.be www.citibank.co.pl www.citibank.ca www.citibank.co.pt www.citibank.cc www.citibank.co.th www.citibank.ch www.citibank.co.tv www.citibank.cl www.citibank.co.tw www.citibank.co.at www.citibank.co.uk www.citibank.co.cc www.citibank.co.vi www.citibank.co.cx www.citibank.co.ws www.citibank.co.dk www.citibank.com www.citibank.co.id www.citibank.com.ar www.citibank.co.in www.citibank.com.au www.citibank.co.io www.citibank.com.bh www.citibank.co.jp www.citibank.com.bi www.citibank.co.ke www.citibank.com.br - 10 - Breaking into computer networks from the Internet [Roelof Temmingh & SensePost]