America Online says it's blocked more than 1 billion virus-infected e-mails since launching a screening program in April 2003.
The Internet service provider, a subsidiary of Time Warner, says it protected each of the company's subscribers from an average of 30 virus attacks.
"As we move into a high-speed world, antivirus protection becomes even more critical, because a basic broadband connection can leave you defenseless against hackers and virus attacks on your home computer," Tatiana Gau, chief trust officer and senior vice president for integrity assurance at AOL, said in a statement.
The Time Warner subsidiary screens both incoming and outgoing mail for free and offers additional fee-based services through a deal with Network Associates, which will soon be renamed McAfee, after its best-known product.
Virus and worm attacks are on rise, according to a survey released in March by TruSecure's ICSA Labs. The 300 companies surveyed said about 11 percent of their computers were infected at any given time during 2003.
This year has also been a busy one for virus writers, who this month released Sasser and Wallon.
During the peak of the Sobig.F outbreak in August 2003, AOL hit its own peak--for viruses blocked in a single day: 24 million in just 24 hours. The virus led the list of the five most pervasive viruses over the last year, followed by MyDoom, Netsky.A, Netsky.D and Swen.