A former programmer has been convicted of planting a computer ``virus'' in his employer's system that wiped out 168,000 records and was activated like a time bomb, doing its damage two days after he was fired. Tarrant County Assistant District Attorney Davis McCown said he believes he is the first prosecutor in the country to have someone convicted for destroying computer records using a ``virus.'' ``We've had people stealing through computers, but not this type of case,'' McCown said. ``The basis for this offense is deletion.'' ``It's very rare that the people who spread the viruses are caught,'' said John McAfee, chairman of the Computer Virus Industry Association in Santa Clara, Calif., which helps educate the public about viruses and find ways to fight them. ``This is absolutely the first time'' for a conviction, McAfee said. ``In the past, prosecutors have stayed away from this kind of case because they're too hard to prove,'' McCown said Tuesday. ``They have also been reluctant because the victim doesn't want to let anyone know there has been a breach of security.'' Donald Gene Burleson, 40, was convicted Monday of charges of harmful access to a computer, a third-degree felony that carries up to 10 years in prison and up to $5,000 in fines. A key to the case was the fact that State District Judge John Bradshaw allowed the computer program that deleted the files to be introduced as evidence, McCown said. It would have been difficult to get a conviction otherwise, he said. The District Court jury deliberated six hours before bringing back the first conviction under the state's 3-year-old computer sabotage law. Burleson planted the virus in revenge for his firing from an insurance company, McCown said. Jurors were told during a technical and sometimes-complicated three-week trial that Burleson planted a rogue program in the computer system used to store records at USPA and IRA Co., a Fort Worth-based insurance and brokerage firm. A virus is a computer program, often hidden in apparently normal computer software, that instructs the computer to change or destroy information at a given time or after a certain sequence of commands. The virus, McCown said, was activated Sept. 21, 1985, two days after Burleson was fired as a computer programmer, because of alleged personality conflicts with other employees. ``There were a series of programs built into the system as early as Labor Day (1985),'' McCown said. ``Once he got fired, those programs went off.'' The virus was discovered two days later, after it had eliminated 168,000 payroll records, holding up company paychecks for more than a month. The virus could have caused hundreds of thousands of dollars in damage to the system had it continued, McCown said. The defense argued during trial that Burleson was set up by someone using his terminal and code. Burleson's attorneys tried to prove he was vacationing in another part of the state with his son on the dates in early September when the rogue programs were entered into the system. But prosecutors presented records showing that Burleson was at work and his son at school on those dates. Defense lawyer Jack Beech maintained Burleson is innocent and but said his client might not have enough money to appeal. Besides, Beech said, Burleson is likely to get the minimum sentence of two years' probation. McCown said he is hoping for a stiffer sentence. Bradshaw on Tuesday ordered a presentence investigation and set sentencing Oct. 21. Burleson already has lost a civil case waged against him by USPA in connection with the incident. The jury in that case ordered him to pay $12,000 to his former employers. McAfee said his organization had documented about 250,000 cases of sabotage by computer virus.