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Press Release

California Man Sentenced for Developing Malware and Infecting Computers

For Immediate Release
U.S. Attorney's Office, Western District of Pennsylvania

PITTSBURGH - A resident of Santa Clara, California, has been sentenced in federal court to 24 months’ probation on his conviction of accessing a protected computer without authorization and initiating spam messages, Acting United States Attorney Soo C. Song announced today.

United States District Judge Arthur J. Schwab imposed the sentence on Sean Tiernan, age 29, of Santa Clara California.

According to information presented to the court, Tiernan, from his computer located in California, was involved in the development of malware, or a malicious computer program, which was programmed to infect computers at a rapid rate by spreading through the computer users’ use of social networking websites. Once a computer was infected with the malware, the malware was programmed by Tiernan to automatically communicate and receive direction from servers over the Internet which were controlled by Tiernan, without knowledge of the infected computers’ owners. The servers which the infected computers called back to were, in and of themselves, previously ‘hacked’, and were also being used without the knowledge of their legitimate owners. The combination of these hacked servers and malware-infected computers formed what is known as a "botnet”. This botnet was controlled by Tiernan and was used to transform the infected victims’ computers into proxy computers from which a high volume of spam (commercial electronic mail) messages could be sent over the Internet to other computers. Since on or about at least August 1, 2011, Tiernan would sell access to his botnet to those who sought to send out these commercial electronic email messages for their own personal commercial gain. At the time of the search of Tiernan's residence and computer via a search warrant on or about October 1, 2012, over 77,000 bots, or infected computers, were active in Tiernan's botnet. Each of these computers, along with the hacked servers used to control them, necessarily were “protected” computers because they were accessed over the Internet in order to be compromised without the owners’ consent. Several of these infected computers in Tiernan's botnet were located in the Western District of Pennsylvania.

Assistant United States Attorney James T. Kitchen prosecuted this case on behalf of the government.

Acting United States Attorney Song commended the Federal Bureau of Investigation for the investigation leading to the successful prosecution of Tiernan.

Updated October 30, 2017