BT is installing software which will enable it to prevent spam attacks before they even reach its broadband customers. 

The Content Forensics spam detection system from StreamShield Networks scans millions of emails a day, providing BT with detailed reports on the location and size of spam-related problems originating from the BT network. 

BT's Customer Security team can then take action against professional spam operators, which could include terminating rogue accounts and adding offending IP addresses to industry-wide blacklists.

According to BT, around 80 per cent of emails sent over the internet, equivalent to 6.5 billion emails a day, are spam.

A large proportion of spam comes from botnets, networks of broadband-enabled PCs previously infected with Trojans which enables them to be controlled remotely by criminals to send spam or launch other attacks.

The anti-spam software will enable BT to disassemble botnets recruited from among its broadband customers by helping them clean the Trojans from their PCs.

While BT's move will undoubtedly benefit its broadband customers and, indeed, all internet users, it will also prevent BT's bandwidth from being wasted on spam and botnet traffic.

Security firm MessageLabs has been lobbying recently for ISPs to filter spam before it reaches consumers, arguing that ISPs have a responsibility to provide a 'clean' supply similar to that expected of water companies.