Despite careful application of best and safest computing practices, and application of available preventive measures – which means installing, using, and keeping screeners, spyware blockers, and scanners up to date – some PCs are unlucky enough to get exposed to new or as-yet documented sources of infection and infestation.

When that happens, such as exposed PC may indeed “catch” something unless the various spyware blockers at work recognize that something potentially dangerous is present and ends up screening or blocking in anyway. This often happens with a Trojan or worm comes along, provided it’s enough like its counterpart for the blocker to recognize it.

But just for grins, assume that something new, undocumented, and virulent comes along and that all software in place doesn’t detect its evil design and purpose. If that software somehow gets executed on a PC to which it has gained access, infestation or infection will probably occur. That’s when the unlucky PC’s user might notice some of the symptoms such as sluggish performance, unexpected changes to defaults or other program settings, sudden stoppage of antivirus, anti spyware, or other security software. This reflects a grim reality on desktops everywhere, as thousands of machines are infested daily.

When that happens, it’s time to scan your system for infection. If you have scanners or spyware blockers installed, download the most recent set of updates, and then use them. In the vast majority of cases, something will turn up, and you’ll quickly get some idea of what’s moved onto your system, along with advice on how to deal with that situation.