User manual

Viruses and more
Avira Professional Security - User Manual (Status: 14 Dec. 2012) 87
Polymorph viruses
Polymorph viruses are the real masters of disguise. They change their own programming
codes - and are therefore very hard to detect.
Program viruses
A computer virus is a program that is capable of attaching itself to other programs after
being executed and cause an infection. Viruses multiply themselves unlike logic bombs
and Trojans. In contrast to a worm, a virus always requires a program as host, where the
virus deposits its virulent code. The program execution of the host itself is not changed as
a rule.
Rootkits
A rootkit is a collection of software tools that are installed after a computer system has
been infiltrated to conceal logins of the infiltrator, hide processes and record data -
generally speaking: to make themselves invisible. They attempt to update already installed
spy programs and reinstall deleted spyware.
Script viruses and worms
Such viruses are extremely easy to program and they can spread - if the required
technology is on hand - within a few hours via email round the globe.
Script viruses and worms use one of the script languages, such as Javascript, VBScript
etc., to insert themselves in other, new scripts or to spread themselves by calling operating
system functions. This frequently happens via email or through the exchange of files
(documents).
A worm is a program that multiplies itself but that does not infect the host. Worms cannot
consequently form part of other program sequences. Worms are often the only possibility
to infiltrate any kind of damaging programs on systems with restrictive security measures.
Spyware
Spyware are so called spy programs that intercept or take partial control of a computer's
operation without the user's informed consent. Spyware is designed to exploit infected
computers for commercial gain.
Trojan horses (short Trojans)
Trojans are pretty common nowadays. Trojans include programs that pretend to have a
particular function, but that show their real image after execution and carry out a different
function that, in most cases, is destructive. Trojan horses cannot multiply themselves,