- An infected computer always will behave differently from its normal state, and you may not be able to boot your system, or it may slow down to a crawl.
- There will be strange or unfamiliar messages or graphics on your screen, and you may be unable to reverse these changed display settings. The programs that you use everyday may start acting funnily.
- There may be a sudden rise in the current data traffic going out of your PC, even when you are not actually on the Internet.
- Files may start removing from your hard disk, and your machine may start sending out spam or other malicious emails to all your email contacts without your knowledge.
- Viruses can be hard to detect, and are more likely to work quietly in the background rather than give you any immediate indication of their presence. Things like your system slowing down or your hard drive space being chewed up can happen for a number of other reasons as well.
When you begin to suspect that your PC is infected, you should take it off the local as well as the Internet or unplug the network cable altogether.