Spam-Proof Your In-Box

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Spam Tips: Let Your Internet Provider Do the Blocking

Don't want to pay for spam filtering software? You might want to consider using the mail scrubbing tools that your ISP provides instead. If you use a major national ISP, the company's filter can screen out as much junk as the average desktop filtering app--if you take the time to train it. Here's a roundup of tools and techniques that the national ISPs use to remove spam from their customers' in-boxes.

EarthLink's SpamBlocker lets the customer choose how aggressively the ISP should filter spam. The lowest level lets everything through; the middle level uses Brightmail. (In InfoWorld tests, Brightmail's spam-filtering accuracy averaged 96 percent, with a false-positive rate of less than 1 percent.) The highest level permits only messages from senders in the user's address book.

United Online (the parent company of NetZero, Juno, and BlueLight) uses content filters (tools that scan the subject and body of messages for keywords), whitelists, blacklists, and a spam reporting system.

MSN Premium and Plus and Hotmail use Brightmail as well as a Microsoft filtering tool that you train over time. MSN Premium and Plus offer five levels of filtering for junk e-mail; the highest level allows an MSN customer to get e-mail only from people listed in the user's MSN address book.

SBC Yahoo's Anti-Spam Resource Center provides a personalized filter that augments systemwide filtering. SBC uses a Real-time Blackhole List, detects and blocks spam servers not yet on the RBL, and blocks any computer on SBC's DSL network that sends mass amounts of e-mail.

At press time, DSL ISP Speakeasy said that it was switching to a tool based on the open-source SpamAssassin (which, in tests for InfoWorld, cleaned out spam e-mail with 93 percent accuracy).

Cox Communications, a cable ISP, uses filters (visit for more information) based on Brightmail.

Cable ISP Adelphia Communications scans its network for customer PCs that are vulnerable to takeover by spammers. It also filters with Brightmail and uses RBLs to cut off spam-friendly networks.

Comcast Communications, another cable ISP, uses a combination of several commercial products that the company rep declined to name. In addition, the company probes its network for spam zombies--PCs that are being controlled by spammers without the owners' knowledge. If the probe discovers a zombie PC, Comcast notifies the customer first; then if the problem doesn't get fixed, it cuts off Internet service temporarily until the enslaved PC can be dezombified.

Logan G. Harbaugh, a freelance writer based in Redding, California, tests spam filtering tools for InfoWorld and PC World.
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