Worms, Trojans, Spyware

Malware: a general class of bad (malicious) software. Malware includes types including:

Worms | Trojan Horses | Spyware | Viruses

Trojan Horses

Trojans are malicious software that gets into a system by pretending to be something desirable, but in fact gives unauthorised access the the victim's operating system. Users are usually tricked into installing a Trojan.

Payload:

Once infected by a Trojan, it burrows into the depths of your system and actively hides itself from detection: some even try to disable your antivirus and firewall protection.

Adware: A trojan may modify the victim's computer to display advertisements in places, such as the desktop or in uncontrollable pop-ups, or may install a toolbar on to the user's Web browser without permission.

They carry out nefarious deeds such as:

- installing keyboard loggers, which record when you type in bank account details, passwords, credit card numbers etc. When the log is full, the trojan uses its built-in email software to "phone home" and pass your sensitive information to the hacker.

- acting as a spam distributor: when the spam is detected, your ISP account gets cancelled, not the hacker's!

- participating in distributed denial of service attacks.

Trojans may carry similar payloads to worms.

Trojans can be installed through:

• Infected software downloads
• Bundling (e.g. as an inconspicuous part of a pirated application downloaded from a torrent site)
• Email attachments
• Websites containing executable content (e.g. an ActiveX control)
• Exploiting flaws in browsers, media players, IM clients, etc to allow installation of a Trojan)

Spread: Trojans can be spread by misleading computer users into installing it, or by installing itself by exploiting system weakness.

According to a 2009 survey conducted by BitDefender, "Trojan-type malware is on the rise, accounting for 83-percent of the global malware detected in the world"

The origin of the term is the legend of the wooden horse at seige of Troy.