The "MyDoom" or "Novarg" virus launched the attack early on Sunday with hundreds of thousands of requests, which crippled the site, SCO spokesman Blake Stowell said.
And with that, MyDoom became the most damaging malware of all time, causing an estimated US$38.5bn of economic damage worldwide since its launch a week ago.
According to mi2g, a global risk management firm, MyDoom is now estimated to have caused $38.5bn of economic damage worldwide in terms of overtime payments, contingency outsourcing, loss of business, bandwidth clogging, productivity erosion, management time reallocation, cost of recovery and software upgrades.
The virus was spread last week by e-mail and caused infected computers to launch the electronic attack against SCO, which has been targeted at least twice this year with such attacks because of its threats to sue users of the Linux operating system in an intellectual property dispute.
On Tuesday, Lindon, Utah-based SCO announced a $250 000 reward for information leading to the arrest and conviction of MyDoom's creator. Stowell said the company believes someone within the Linux community is behind the worm.
Sunday's attack had a higher profile because the well-publicised MyDoom virus was involved, but that doesn't make the assault unique, a computer expert said.
Internet traffic to SCO's website began building late on Saturday night, and overwhelmed it just after 05:00 on Sunday.
The attack is programmed to continue on SCO's website until February 12, according to messages left inside the virus' code.
But the company said it would announce a contingency plan on Monday for customers to access the site.
It will likely involve slightly altering the wording SCO's web-address, said David Perry, a spokesman for antivirus firm Trend Micro.
The strain that shut down SCO's website was the MyDoom.A virus. Another strain, called MyDoom.B, is set to launch an attack on Tuesday on Microsoft.
The companies have been sharing information about the virus and how each is addressing it. Microsoft also has offered a $250 000 reward to help catch those behind the virus.
With the recent developments and proliferation, MyDoom has surpassed the destruction of Sobig - the second worst malware of all time, which caused $37bn of economic damage worldwide in 2003.
The ranking table, according to mi2g, of the top ten worst malware of all time showing the mid point of economic damage in brackets is as follows:
- MyDoom ($38.5bn)
- Sobig ($37.1bn)
- Klez ($19.8bn)
- Mimail ($11.5bn)
- Yaha ($11.5bn)
- Swen ($10.4bn)
- Love Bug ($8.8bn)
- BugBear ($3.9bn)
- Dumaru ($3.8bn)
- SirCam ($3.0bn)
On the Net: