A top government cybersecurity official who secretly joined an online pedophile network to swap child sex abuse material and rape fantasies has been convicted.

Timothy DeFoggi, 56, is described by the US Department of Justice as being the former acting director of cyber security at Uncle Sam's Department of Health and Human Services. He was arrested, charged and brought to trial in Nebraska after the FBI investigated three child abuse websites – and found he had signed up as a member to at least one of them.

Court documents state he joined one of the sites in March 2, 2012, and was active on it until December 8, 2012, when the FBI shut the site down. They state he saw sexual images of children, asked others on the site for them and exchanged messages with other site members about taking part in abuse personally.

The prosecution said that DeFoggi went as far as to suggest meeting another member of the website "to fulfill their mutual fantasies to violently rape and murder children," the DOJ states.

According to the Omaha World-Herald DeFoggi was a member of the Pedobook website and told an undercover investigator that he liked to visit the site in the early hours of the morning when he was unlikely to be disturbed. Law enforcement officials broke into his house at 5.30am on April 2013 and found him in the act of hunting for new child abuse images.

DeFoggi admitted using Tor to access the dark web but denied any involvement in child abuse. He said he was looking for servers that contained information that could be harmful to national security, such as the Edward Snowden files.

His lawyer claimed investigators didn't find any of the vile images on computers at his home, but the prosecution said that he had used specialized software to erase them from his systems.

After the trial jury deliberated for two hours, DeFoggi was convicted of engaging in a child exploitation enterprise, conspiracy to advertise and distribute child pornography, and accessing a computer with intent to view child pornography. Sentencing will be carried out in early November. ®