Botnet, Zombie Army, Bot Army
Any number of computers which have been programmed without their owners’ knowledge to forward transmissions to other computers on the Internet.
Current estimates are that at least 20-50 million computers worldwide have been infected and are part of over 50,000 botnets, including personal and corporate computers.
Nearly all spam mail is
transmitted by botnets. The controller (also handler or herder) of a
zombie army usually gains access to a computer through a
port which
has been left open or through an opened e-mail attachment or from a
clickable image.
Typically, a Trojan horse program is left for future activation,
then at a set time, the controller unleashes the effects of the army
by sending a single command, which is virtually untraceable.
Sometimes the malware comes to life when a specific application is
opened, such as Word, for which the exploit was custom-tailored. A
newer technique uses a very small program called a “dropper” to gain
access to a computer and later admit the malware.
Massive e-mail attacks are one of many malicious uses, but more
profitable are denial of service extortion (sending so much traffic
to a site that a site can’t receive legitimate visitors and the site
then pays to stop the attack), stock trading scams (which pump up
the value of a penny stock by massive hyping then dumping of the
stock) and identity theft (stealing personal information and selling
it on the black market).
Rival bot armies even attempt to take over each other’s computer territory by hijacking and re-routing computers to their own army by exploiting flaws in their rivals’ malware. E-mail precautions, a good firewall, frequent use of anti-spyware software, and not leaving your cable modem on all-night are all sensible steps to take.