TNT is not a virus, but an antivirus program. If F-Secure
anti-virus products say that a program has been modified by Turbo
Antivirus, it means that Turbo Antivirus has added a self-checking
module to the end of the program.
When a program modified in this way is executed, the added code
will first check that the length of the program is not changed,
and allows the program to execute only if this is not the case.
F-Secure anti-virus products detect programs modified in this way
because the added code resembles virus code closely, and also because
several programs (including F-Secure anti-virus products) will not
run after a modification like this.
