A fresh attack by a long-known hacking group suspected to be linked with Russia did little to mask its activity in an attack a week ago.

The computer security firm FireEye wrote on Saturday that the group — called APT 28 — attacked an “international government entity” on April 13, using two recently disclosed software flaws, one of which has not been patched.

The attack sought to trick victims into clicking on a link that led to a website which attacked their computer. It first used a vulnerability in Adobe Systems’ Flash player, CVE-2015-3043, then used a still unpatched Microsoft vulnerability, CVE-2015-1701, to gain higher privileges on a computer.

In a white paper released last year, FireEye said APT 28 had conducted attacks against political and military-related organizations since at least 2007. The group compiles “malware samples with Russian language settings during working hours consistent with the time zone of Russia’s major cities, including Moscow and St. Petersburg.”

The malware delivered in the latest attack is very similar to CHOPSTICK, a backdoor known to be used by APT 28. In fact, the malware delivered in the latest attack used the same RC4 encryption key that was used by CHOPSTICK, FireEye said.

Even hacking groups considered to be sophisticated often reuse infrastructure or components, which over the long term help security researchers identify their attacks. FireEye also said the latest malware connects to the same command-and-control infrastructure that APT 28 has used.

The exploit used by APT 28 won’t work if users have upgraded to the latest Flash version released on Tuesday, so administrators are advised to patch.

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