Trojan horses can be bad. Very bad. But what exactly do they do? I’ve written before about how there are now 6 distinct types of Trojan but these parasites generally tend to perform just one of two main functions –
Watchers and Monitors
Trojans that fall into this category are predominantly information gatherers which will attempt to gain as much information about you are your surfing habits as they possibly can.
The monitoring site behind such a Trojan will then attempt to use this information for their own financial gain.
The writer of a Trojan can make money from this information in a couple of different ways.
One is to use it in order to direct the computer user to sales pages which offer products that are related to the types of searches that they conduct online.
The other is to simply sell such information on to other interested parties.
Such Trojans are often well written and have no other adverse effect upon they systems which they reside on.
This is because they don’t wish to be conspicuous – after all, they longer they remain on a system, the more information that they can gather.
Thieves and Hijackers
The other main function of Trojans is far more malicious in nature.
Hackers use Trojans in order to gain access to your system for far more nefarious purposes.
Such Trojans allow other programs to be introduced to a system, such as keystroke loggers, which then allow the hacker to acquire sensitive information such as online banking passwords that they can use to steal from you.
Alternatively, the hacker may use a Trojan to gain access in order to then run other programs or functions such as a Denial of Service attack.
Again, this is of financial benefit to them as DDOS attacks are no longer just about knocking a competitor’s site out for a while, they are big business with certain individuals and organisations offering such attacks on demand in return for a financial incentive.