The advanced persistent threat (APT) actor known as Winter Vivern is now targeting officials in Europe and the U.S. as part of an ongoing cyber espionage campaign.

“TA473 since at least February 2023 has continuously leveraged an unpatched Zimbra vulnerability in publicly facing webmail portals that allows them to gain access to the email mailboxes of government entities in Europe,” Proofpoint said in a new report.

The enterprise security firm is tracking the activity under its own moniker TA473 (aka UAC-0114), describing it as an adversarial crew whose operations align with that of Russian and Belarussian geopolitical objectives.