A detection name that uses the format "trojan.generic.[variant]" is a Generic Detection that identifies files with trojan-like characteristics or behavior.
Named after the Trojan Horse of Greek legend, a trojan is a malicious program that performs, or appears to perform, one function, but in reality executes another action without the user's knowledge or consent.
Quite often, the trojan will either have or pretend to have a functionality that offers a useful service to the user - like a screensaver, a utility program, a service pack or application update and so on - in order to encourage the user to install the trojan.
Once the trojan is installed however, it performs its actual, unauthorized function, which ranges from mildly annoying pranks (like changing desktop icon positions), to serious, user-inhibiting functions (like disabling the keyboard or mouse) to critically destructive actions (like erasing files or stealing data).
The majority of trojans today carry a payload designed to cause harm.
About Generic Detections
Unlike more traditional detections (also known as signatures or single-file detections) a Generic Detection does not identify a unique or individual malicious program. Instead, a Generic Detection looks for broadly applicable code or behavior characteristics that indicate a file as potentially malicious, so that a single Generic Detection can efficiently identify dozens, or even hundreds of malware.
For more information about Generic Detections, see the Generic Detection description.