Hackers have spread seven new variants of the Spamta worm, it was reported today.

The worm attaches itself to emails posing as email delivery error messages and attempts to entice users into clicking on a malicious attachment.

According to reports creators of the worm have put numerous strains in circulation in a short period of time, increasing the probability of a computer becoming infected. Variations include the size or compressed format of the files that contain the virus and the files that they copy to affected computers.

This fresh batch of worms comes just one month after the previous set, in which hackers released around 67 variants.

Luis Corrons, director of virus research company PandaLabs, said: "It would seem that the creators of Spamta are determined to saturate the internet with hundreds of variants, although their ultimate objective is not very clear.

"We believe that the strategy could be to get users and security companies so accustomed to these worms that they drop their guard, and then the creators can strike by putting far more dangerous variants in circulation."