Trojans [a malicious programme that is disguised as or embedded within legitimate software] are known to be sneaky and stubborn but do not spread on their own. And they are becoming stealthy exploits, according to reports from a variety of security vendors and researchers.
Most trojans today spread via spam email and malicious websites (primarily those that offer free downloads and wallpapers). But what scares researchers most is the fact that they are increasingly being used for more sophisticated and targeted attacks. The new Internet Explorer exploit that’s rapidly spreading is reportedly installing trojans.

A trojan is designed to do nefarious things like allow other users to gain access to your computer or to do damage in conjunction with a virus, such as deleting files. The most popular family of trojans today are the so-called Banker trojans. According to a report, there were 4,000 unique types of Banker trojans reported in 2005, which has spiked to 6,000 this June.

Another prominent family of trojans is the Downloader clan, of which there are around 30 variants. Then there are the growing number of Haxdoor backdoor trojans, which are built from a hacker tool of the same name. Haxdoor trojans are sometimes used to steal sensitive data and are especially difficult to detect.

The point is increasing number of trojans overall is making it harder to detect them, but security experts say the bigger issue is their increasing sophistication in stealing data. Websense’s site claims that Banking/Banker is one such trojan used for stealing data from individuals and then delivering that information to third parties.

We all know that attackers take advantage of Microsoft’s monthly patch cycle by launching similar exploits between patches. With the new IE bug, which leverages a vulnerability in the Vector Markup Language, an attacker basically installs the malware on a website it controls or one it has broken into, and downloads a trojan onto the victimized computer via the Web browser vulnerability.

What’s next? Every kid who has even an iota of interest in computer’s could be springing malware on to the internet.