A logic bomb is a piece of code intentionally inserted into a software system that will set off a malicious function when specified conditions are met. For example, a programmer may hide a piece of code that starts deleting files (such as a salary database trigger), should they ever be terminated from the company. Software that is inherently malicious, such as viruses and worms, often contain logic bombs that execute a certain payload at a pre-defined time or when some other condition is met. This technique can be used by a virus or worm to gain momentum and spread before being noticed. Some viruses attack their host systems on specific dates, such as Friday the 13th or April Fools' Day. Trojans and other computer viruses that activate on certain dates are often called "time bombs". To be considered a logic bomb, the payload should be unwanted and unknown to the user of the software. As an example, trial programs with code that disables certain functionality after a set time are not normally regarded as logic bombs. Successful In June 2006 Roger Duronio, a system administrator for UBS, was charged with using a logic bomb to damage the company's computer network, and with securities fraud for his failed plan to drive down the company's stock with activation of the logic bomb. Duronio was later convicted and sentenced to 8 years and 1 month in prison, as well as a $3.1 million restitution to UBS. On 20 March 2013, in an attack launched against South Korea, a logic bomb struck machines and "wiped the hard drives and master boot records of at least three banks and two media companies simultaneously." Symantec reported that the malware also contained a component that was capable of wiping Linux machines. On 19 July 2019, David Tinley, a contract employee, pleaded guilty for programming logic bombs within the software he created for Siemens Corporation. The software was intentionally made to malfunction after a certain amount of time, requiring the company to hire him to fix it for a fee. The logic bombs went undetected for two years, but was then discovered while he was out of town and had to hand over the administrative password to his software. Attempted In February 2000, Tony Xiaotong Yu, indicted before a grand jury, was accused of planting a logic bomb during his employment as a programmer and securities trader at