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 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.
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 126.96.36.199 2 Async 188.8.131.52 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:
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:
"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.
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)
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
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)
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.