Chameleon

Chameleon is a powerful program designed to fool Monitor programs and kill software. When carried, it works just like a simple Killer-IV. When it kills a program. it reconfigures it's code and appearance until it resembles the program it has just killed. When a Chameleon is encountered by a Monitor (or a Sysop), the Monitor must make a STR (Interface) + 1D10 roll versus the Chameleon's roll (STR 4 + 1D10) to notice that anything is wrong. It must make this roll every time it is encountered.

Source

 * Rache Bartmoss Guide to the Net, pg.148