A notorious cyber espionage group has been using a Java zero-day exploit in attacks aimed at the armed forces of a NATO member country and a defense organization based in the United States, Trend Micro reported over the weekend.

According to researchers, the unpatched Oracle Java SE remote code execution vulnerability has been leveraged by the group known as Pawn Storm, APT28, Sednit, Fancy Bear, Tsar Team, and Sofacy. Experts have pointed out that this is the first Java zero-day attack reported after nearly two years.

Trend Micro has not released any technical information on the Java zero-day. The security firm noted that the vulnerability affects the latest version of Java, 1.8.0.45, but older versions such as 1.6 and 1.7 are not impacted. Oracle is working with Trend Micro on analyzing the threat.

In the attacks on the NATO member country and the US defense organization, the attackers sent out emails that contained links to malicious domains hosting the Java exploit (JAVA_DLOADR.EFD). The exploit is designed to deliver a Trojan dropper (TROJ_DROPPR.CXC) that drops a payload detected as SPY_FAKEMS.C to the “login user” folder.

Update: Oracle Patches Java Zero-Day, 192 Other Security Bugs

Experts have pointed out that the domains hosting the Java zero-day exploit are similar to the ones used in April 2015 in attacks targeting NATO members and the White House.

Pawn Storm, which is said to have Russian roots, has been around since at least 2007. The advanced persistent threat (APT) actor has targeted military, government, media and defense organizations from across the world. In some of its attacks, the group targeted nation-state organizations using the Asia-Pacific Economic Cooperation (APEC) Forum, the Middle East Homeland Security Summit 2014 and other political events as part of its social engineering tactics.

Trend Micro has highlighted that the Java zero-day used by Pawn Storm is not related to the recent Hacking Team breach in which at least three Adobe Flash Player and one Microsoft Windows zero-day bugs have been leaked.

However, ESET reported last week that the Pawn Storm cyber espionage group, which the security firm calls Sednit, was one of the several APT actors abusing the first Flash Player (CVE-2015-5119) exploit discovered in the Hacking Team leak.

According to ESET, the group used the Flash Player exploit to target institutions in Eastern Europe.