A record 36,039 cases of computer worm and virus infections were reported in the January-June period, antivirus software maker Trend Micro Inc. said Friday.
The Netsky worm caused the greatest number of infections, at 4,186 cases, followed by Bytever, with 1,355 cases, it said.
The Netsky enters personal computers when users open files attached to e-mails originating from the creator of the worm. The Bytever can slip into computers when users browse certain Web sites.
The previous half-year record for computer virus infections was 30,581 cases in the second half of 2003, when the MSBlast worm hit the personal computer community, Trend Micro said.
Vaccine-software makers are planning to introduce fixed-rate defense services, under which computer users will pay an annual sum to have the makers automatically update vaccine software to ward off new types of worms.