Proofpoint has disclosed details of a targeted email campaign in which threat actors with ties to Russia are leveraging the recently disclosed DarkSword exploit kit to target iOS devices.
The activity has been attributed with high confidence to the Russian state-sponsored threat group known as TA446, which is also tracked by the broader cybersecurity community under the monikers Callisto, COLDRIVER, and Star Blizzard (formerly SEABORGIUM). It’s assessed to be affiliated with Russia’s Federal Security Service (FSB).
The hacking group is known for spear-phishing campaigns aimed at harvesting credentials from targets of interest. However, attacks mounted by the threat actor over the past year have targeted victims’ WhatsApp accounts, as well as leveraged various custom malware families to steal sensitive data.
The latest activity, highlighted by Proofpoint and Malfors, involves using fake “discussion invitation” emails spoofing the Atlantic Council to facilitate the delivery of GHOSTBLADE, a dataminer malware, via the DarkSword exploit kit. The emails were sent from compromised senders on March 26, 2026. One of the email recipients was Leonid Volkov, a prominent Russian opposition politician and the political director of the Anti-Corruption Foundation.
An automated analysis triggered by Proofpoint’s security tools is said to have redirected to a benign decoy PDF document, likely because of server-side filtering put in place to only lead iPhone browsers to the exploit kit.
“We have not previously observed TA446 target users’ iCloud accounts or Apple devices, but the adoption of the leaked DarkSword iOS exploit kit has now enabled the actor to target iOS devices,” Proofpoint said.
The enterprise security firm also noted that the volume of emails from the threat actor has been “significantly higher” in the last two weeks, adding that these attacks lead to the deployment of a known backdoor referred to as MAYBEROBOT via password-protected ZIP files.
The group’s use of DarkSword has also been corroborated by the fact that a DarkSword loader uploaded to VirusTotal has been found to reference “escofiringbijou[.]com,” a second-stage domain attributed to the threat actor.
A urlscan.io result has revealed that the TA446-controlled domain has served the DarkSword exploit kit, including the initial redirector, exploit loader, remote code execution, and Pointer Authentication Code (PAC) bypass components. However, there is no evidence that sandbox escapes were delivered.
It’s suspected that the TA446 is repurposing the DarkSword exploit kit for credential harvesting and intelligence collection, with Proofpoint noting that the targeting observed in the email campaign was “much wider than usual” and that it included government, think tank, higher education, financial, and legal entities.
This, in turn, has raised the possibility that the threat actor is leveraging the new capability afforded by DarkSword as part of an opportunistic campaign against a broader target set.
Greg Lesnewisch, staff threat researcher at Proofpoint, told The Hacker News that the attack likely leveraged a leaked version of DarkSword, which was taken directly from one of UNC6353’s watering holes and uploaded to GitHub, and that “TA446 is using the same version of the exploit kit UNC6353 was using.” It’s currently not known if any of these attacks were successful. However, Proofpoint said all messages targeting its customers were blocked.
The development comes as Apple has begun sending Lock Screen notifications to iPhones and iPads running older versions of iOS and iPadOS to alert users of web-based attacks and urging them to install the update to block the threat. The unusual step signals that the company is treating it as a broad enough threat requiring users’ immediate attention.
Apple’s warning also coincides with the leak of a new version of DarkSword on GitHub, raising concerns that they could democratize access to nation-state exploits, fundamentally shifting the mobile threat landscape.
Justin Albrecht, principal researcher at Lookout, said the leaked, plug-and-play version allows even unskilled threat actors to deploy the advanced iOS espionage kit, turning it into commodity malware.
“DarkSword refutes the common belief that iPhones are immune to cyber threats, and that advanced mobile attacks are only used in targeted efforts against governments and high-ranking officials,” Albrecht added.
