The US firm's ultimatum follows a similar decision by Scandinavian ISP TeliaSonera, which sent warning letters to customers exploited by spammers.
Spammers were reported to have used customers' PCs as 'zombies', which acted as a spam distributor.
Comcast warned customers to keep their PCs clean after some of its IP addresses were discovered on anti-spam blacklists, which stopped some users sending emails.
.jpg&h=140&w=231&c=1&s=0)
.jpg&h=140&w=231&c=1&s=0)
.png&w=100&c=1&s=0)
Cloud Resilience Summit
iTnews Benchmark Security Awards 2026
iTnews State of Security Breakfast Sydney
iTnews Executive Retreat - Security Leaders Edition - VIC
