Application security

ISP email filtering helping win the battle vs. spam

Internet service providers' anti-spam technologies are now capable of blocking the vast majority of spam sent to their email servers, according to a new study released today by the Federal Trade Commission.

The agency studied three aspects of spam: email address harvesting – the automated collection of email addresses from public areas of the internet, the effectiveness of spam filtering by ISPs and the effectiveness of using "masked" email addresses as a technique to prevent the harvesting of addresses.

To conduct the study, FTC staff created 150 new undercover email accounts – 50 at an ISP that uses no anti-spam filters and 50 each at two different ISPs that use spam filters. They then posted the email addresses on 50 internet sites, including message boards, blogs, chat rooms and USENET groups where spammers might go to attempt to harvest the addresses.

The study concluded that spammers continue to harvest email addresses posted on web sites, but addresses posted in chat rooms, message boards, USENET groups, and blogs were unlikely to be harvested.

"Indeed, some chat room operators took proactive measures to prevent the harvesting of email addresses posted by the FTC staff," the study stated.

After a five-week trial, email addresses at the unfiltered ISP received a total of 8,885 spam messages. At the end of the same period, email addresses at one of the ISPs that uses filtering technologies received a total of 1,208 spam messages and email addresses at the second ISP that uses filtering technologies received a total of 422 spam messages. The filter of the first ISP blocked 86.4 percent of the spam, and the filter of the second ISP blocked 95.2 percent of the spam.

The study also tested whether using "masked" email addresses prevents the harvesting of email addresses and consequently reduces spam. "Masking" addresses involves altering an email address to make it understandable to the recipient but confusing to automated harvesting software. For example, an email address such as [email protected] could be altered to appear as john doe at FTC dot gov. The study found that masking email addresses was very effective in thwarting harvesting. After five weeks, unmasked email addresses had received more than 6,400 pieces of spam, while the masked email addresses had received only one piece of spam.

The study concluded that consumers who must post their email addresses on websites can reduce the risk of having their email address harvested – making them a target of spammers – by masking their addresses. It also demonstrated the effectiveness of ISPs' spam filters.

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