An armored virus attempts to make disassembly difficult.

Back Orifice is a Trojan that provides a backdoor into your computer when active and you are connected to the Internet.

Batch files can be used to transmit binary executable code and either be a virus or drop viruses.

A botnet is a network of remote-controlled zombie computers.

A buffer overflow is a programming error that allows data to exist in memory that it should not be allowed to access. This can result in errors or, more seriously, an infection.

When scanners were less sophisticated it might have been possible for a virus to sneak by as scanners sometimes did not display some alarms, knowing them to be false. This type of virus would be extremely hard to write today.

This virus is the classic that illustrates the working and danger of a spacefiller virus type.

Companion viruses make use of a DOS quirk that runs COM files before EXE files. The virus infects EXE files by installing a same-named COM file.

A denial-of-service attack (DoS attack) or distributed denial-of-service attack (DDoS attack) is an attempt to make a computer resource unavailable to its intended users.