Just as hundreds of thousands of people are starting to come down with summer colds and hayfever, so the Internet seems to have caught another nasty virus with the reappearance of a different version of Bugbear.

Earlier this week, SoBig.C swamped the Net, leading many anti-virus specialists to upgrade it to a High risk rating since it was the third version of the virus since the start of the year and a more advanced (and dangerous) version. The same is true for Bugbear.B.

The B version of the virus was first noted in Australia very early this morning but is moving with speed and alarming frequency across the globe as Europe and now the US wakes up. The problem is that Bugbear.B is pretty advanced and varies significantly each time.

It arrives from different spoofed addresses each time (including domains of international banks and government authorities), with a different comment and a differently titled file attached - although it will end in .scr, .pif or .exe. It also contains an auto-open bit of code that will cause the program to automatically run on a Windows system that hasn't been patched as soon the email is read.

The damage it can cause is also worrying. Early reports say it may disarm the PC's security software and it spreads easily through computer networks. Of even more concern, it contains some code that will enables a hacker to not only access the machine but also download a file containing recent keystrokes - meaning that any passwords or credit card details typed in by the PC's user could be picked out and used maliciously.

In short, it is nasty, so look out for it, and try to avoid falling ill so early on the season.