David Smith, creator of the Melissa virus, has been sentenced to 20 months in a federal prison and fined $5,000.

The sentence comes nearly three years after Smith wrote and released the program which caused millions of dollars of damage to computer networks around the world.

In court on Wednesday, the New Jersey resident said that distributing the virus had been a "colossal mistake".

Although he is among the first people ever prosecuted for creating a computer virus, analysts have maintained that the sentence is unlikely to deter similar virus writers in the future.

Forrester analyst Lorna Koetzle said: "It is a stiff sentence akin to a zero tolerance approach, but the people who commit these attacks believe that only the stupid get caught and that they are not stupid.

"There is no good yardstick for crimes of this type, so this looks to have been treated as a kind of vandalism."

The virus, named after a Florida stripper, wreaked havoc on computer systems around the world within hours of its release in March 1999.

Melissa propagated by automatically sending copies of itself to 50 contacts from the host user's Microsoft Outlook address book, with an infected attachment marked 'important message' which was opened using Microsoft Word.

The sheer volume of traffic created by the spread of the virus slowed many systems to a crawl, but analysts have pointed out that subsequent viruses such as Nimda and Code Red have caused far greater damage.

Smith pleaded guilty in December 1999 to a New Jersey state charge of computer theft and to a federal charge of sending a damaging computer program. In the federal case, both sides agreed that the damage was greater than $80m.

Smith could have faced up to five years in prison, but prosecutors suggested a term of about two years, saying that he had given the authorities extensive assistance in thwarting other virus creators.