The U.S. launched a cyber attack against Iranian spy assets in the hours after the Islamic republic downed an American navy reconnaissance drone last week, according to various reports.

U.S. Cyber Command was behind the retaliatory strike against the spy group, which has ties to the Islamic Revolutionary Guard Corps (IRGC).

Yahoo! News first reported the U.S. response, revealing the online strike targeted an Iranian espionage group’s computer software that was also used to track the tankers that were targeted in the Gulf of Oman on June 13.

A spokesman for the Pentagon would not comment on the matter Saturday, saying that “as a matter of policy and for operational security, we do not discuss cyberspace operations, intelligence or planning.”

Three U.S. officials told the Associated Press (AP) the operation on Thursday evening disabled Iranian computer systems that controlled IRGC rocket and missile launchers.

AP reports the officials say defense had prepared such a cyber response as a contingency plan for weeks preceding the attack.

President Donald Trump ordered air and naval strikes against Iranian targets as a first response to the shooting down of the U.S. Navy drone, but later canceled them.

Cybersecurity firms say Iran has increased its offensive cyberattacks against the U.S. government and critical infrastructure as tensions have grown between the two nations over the past month.

CrowdStrike and FireEye, which regularly track such activity, say in recent weeks hackers believed to be working for the Iranian government have targeted U.S. government agencies, as well as sectors of the economy, including oil and gas.

The firms say the hackers have sent waves of phishing emails.

Christopher Krebs, director of the Department of Homeland Security’s Cybersecurity and Infrastructure Security Agency, said in a statement released Saturday his agency “is aware of a recent rise in malicious cyber activity directed at United States industries and government agencies by Iranian regime actors and proxies.”

“We will continue to work with our intelligence community and cybersecurity partners to monitor Iranian cyber activity, share information, and take steps to keep America and our allies safe,” he added. AP contributed to this report