Filtering system protects DB staff from 95pc of unwanted emails

By RICHARD WOOD

DB Breweries says it is blocking 95 per cent of spam since it upgraded its Mailsweeper filtering software three months ago.

The firm averages 60,000 emails a month for its 400 staff and 2000 to 3000 are unsolicited promotional messages or spam.

DB business analyst Jason Chuang said the firm had been getting complaints from staff about the unwanted emails.

"As far as I am concerned it's the new type of virus," he said. "They are quite small but the sheer volume does add up."

He said a lot of the spam was undesirable material promoting x-rated websites and financial scams.

A small number of DB staff were getting a disproportionate amount of spam, depending on where their email address had been used publicly.

Chuang said spammers were getting smarter at getting email addresses, using "robots" to harvest them from insecure websites and mailing lists. They were also getting smart at defeating spam filtering systems.

For example, instead of sending text that could be recognised by anti-spam systems, they might use web-based (HTML) emails with links to web pages or use graphics that looked like text.

DB's approach had led to some "false positives", with one in every few hundred emails quarantined being a genuine business email.

But Chuang said these usually turned out to be relatively unimportant messages. "We haven't had one that has been the end of the world - yet."

Chuang said the help desk was looking at the the spam once a week to spot genuine messages. It did this by checking the sender and receiver details of mail quarantined by the Mailsweeper system.

Chuang said DB was taking two approaches to combating the spam.

One used lexical analysis, where weightings were put on standard words or phrases known to be prevalent in spam messages.

A lot of time had been spent tweaking the weightings and overall tolerance level.

The second approach, called Spamactive, downloaded "fingerprint" updates about current spam messages, similar to an anti-virus system.