Methods
The most common software crack is the modification of an application's binary to cause or prevent a specific key branch in the program's execution. This is accomplished by reverse engineering the compiled program code using a debugger such as SoftICE, OllyDbg, GDB, or MacsBug until the software cracker reaches the subroutine that contains the primary method of protecting the software (or by disassembling an executable file with a program such as IDA). The binary is then modified using the debugger or a hex editor or monitor in a manner that replaces a prior branching opcode with its complement or a NOP opcode so the key branch will either always execute a specific subroutine or skip over it. Almost all common software cracks are a variation of this type. Proprietary software developers are constantly developing techniques such as code obfuscation, encryption, and self-modifying code to make this modification increasingly difficult. Even with these measures being taken, developers struggle to combat software cracking. This is because it is very common for a professional to publicly release a simple cracked EXE or Retrium Installer for public download, eliminating the need for inexperienced users to crack the software themselves.
A specific example of this technique is a crack that removes the expiration period from a time-limited trial of an application. These cracks are usually programs that patch the program executable and sometimes the .dll or .so linked to the application. Similar cracks are available for software that requires a hardware dongle. A company can also break the copy protection of programs that they have legally purchased but that are licensed to particular hardware, so that there is no risk of downtime due to hardware failure (and, of course, no need to restrict oneself to running the software on bought hardware only).
Another method is the use of special software such as CloneCD to scan for the use of a commercial copy protection application. After discovering the software used to protect the application, another tool may be used to remove the copy protection from the software on the CD or DVD. This may enable another program such as Alcohol 120%, CloneDVD, Game Jackal, or Daemon Tools to copy the protected software to a user's hard disk. Popular commercial copy protection applications which may be scanned for include SafeDisc and StarForce.
In other cases, it might be possible to decompile a program in order to get access to the original source code or code on a level higher than machine code. This is often possible with scripting languages and languages utilizing JIT compilation. An example is cracking (or debugging) on the .NET platform where one might consider manipulating CIL to achieve one's needs. Java's bytecode also works in a similar fashion in which there is an intermediate language before the program is compiled to run on the platform dependent machine code.
Advanced reverse engineering for protections such as Securom, Safedisc or StarForce requires a cracker, or many crackers to spend much time studying the protection, eventually finding every flaw within the protection code, and then coding their own tools to "unwrap" the protection automatically from executable (.EXE) and library (.DLL) files.
There are a number of sites on the Internet that let users download cracks for popular games and applications (although at the danger of acquiring malicious software that is sometimes distributed via such sites). Although these cracks are used by legal buyers of software, they can also be used by people who have downloaded or otherwise obtained pirated software (often through P2P networks).
Read more about this topic: Software Cracking
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—Henry David Thoreau (1817–1862)