Sludge3000
Viruses are accidentally infecting worms on victims’ computers, creating super-powered strains of hybrid software nasties.
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All of the malware hybrids analysed by BitDefender so far have been created accidentally. However, the risk posed by these combos could increase dramatically as crooks latch onto the idea of deliberately splicing malware strains together to see what sticks. This is on top of efforts by blackhat coders to add extra features to others' viruses and unleash the updated builds onto the unsuspecting public.
Story @ The Register
Blogpost @ Malware City