Slapper worm's infection rate in Australia has more than doubled this week with around 120 businesses already hit, according to Internet Security Systems (ISS).
ISS principal consultant for Australasia, Grant Slender, said reports of infection escalated from 5500 worldwide to 15,000 in a 24-hour period and three variants of the Slapper worm -- A, B and C -- have now been discovered.
"Virus writers are modifying the worm and adding functionality that could see it emerge as a more sophisticated threat in very little time; it surpassed Code Red in the first few days," he said.
The variants have subtle differences from the first Slapper worm carrying the same attack payload exploiting a previously disclosed vulnerability in the Secure Sockets Layer 2.0 (SSLv2) handshake process. Slapper A, B and C target the Linux operating system running the Apache Web server with OpenSSL.
All versions carry back-door and distributed denial of service functionality with Slender claiming widespread distribution of the code in the hacker community has made it a development platform for future variants.