After Backtrack has improved over time, the developers renamed the distro Kali. The last version of Backtrack is version 5R3. The developers rewrote the system and named it Kali and started the version numbering at 1.0. Both systems are used to test the security strength of a system. However, some people use Kali to maliciously hack systems (this is illegal). Kali can test wireless security, analyze packets, scan ports, etc.