T 0.39 Malicious Software

Malicious software is software developed with the aim of performing unwanted and often harmful operations. Typical kinds of malicious software include viruses, worms and Trojan Horses. Malicious software is usually active in a secret way without the user's knowledge or consent.

Nowadays, malicious software offers an attacker comprehensive communication and control possibilities, and makes a variety of functions available. Amongst other things, malicious software can purposefully reveal passwords, remote-control systems, deactivate data protection software and spy on data.

The most significant damage here is loss or corruption of information or applications. But also the loss of reputation and financial damage, caused by malicious software, are of great importance.

Examples:

• In the past, the malicious software W32/Bugbear was spread in two ways: it searched in local area networks for computers with shares, where write access was possible, and made copies of itself on each share found. Moreover, it sent itself as an HTML-email to recipients in the email address books of infected computers. Due to an error in the HTML routines of certain email programs, the malicious software was executed upon opening the message without further action by the recipient.
• The malicious software W32/Klez spread in different variants. Infected computers sent the virus to all recipients in the email address book of the computer. After this virus had infected a computer, by continuous manipulation of the operating system it prevented the installation of anti-virus programs from most popular manufacturers and made it significantly more difficult to perform disinfection of the infected computers.