Trend reported the Sykipot malware program has been exploiting networks for more than five years. It's still active and the cybersecurity company said it's "being used to gather intelligence about the civil aviation sector in the United States."
Trend and PCWorld last month said they observed increased activity from Chinese hackers. China was accused of targeting U.S. national security networks with cyberattacks, an allegation it denies. Syrian hackers targeted The New York Times last month.
Trend didn't indicate the origin of the Sykipot malware. It said Wednesday the intention of the activity is unclear.
"Since this attack typically arrives via email messages, it is important for organizations to implement a good social engineering program," it said. "This can help organizations, particularly employees, managers etc., to be wary of email messages that may carry malware related to campaigns like Sykipot."
U.S. Army Maj. Gen. John Davis, a policy adviser for the military, said in July cybersecurity was fast becoming one of the country's top national security priorities.