Microsoft Threat Intelligence has uncovered a cyberespionage campaign by the Russian state actor we track as Secret Blizzard that has been targeting embassies located in Moscow using an adversary-in-the-middle (AiTM) position to deploy their custom ApolloShadow malware. ApolloShadow has the capability to install a trusted root certificate to trick devices into trusting malicious actor-controlled sites, enabling Secret Blizzard to maintain persistence on diplomatic devices, likely for intelligence collection. This campaign, which has been ongoing since at least 2024, poses a high risk to foreign embassies, diplomatic entities, and other sensitive organizations operating in Moscow, particularly to those entities who rely on local internet providers.
While we previously assessed with low confidence that the actor conducts cyberespionage activities within Russian borders against foreign and domestic entities, this is the first time we can confirm that they have the capability to do so at the Internet Service Provider (ISP) level. This means that diplomatic personnel using local ISP or telecommunications services in Russia are highly likely targets of Secret Blizzard’s AiTM position within those services. In our previous blog, we reported the actor likely leverages Russia’s domestic intercept systems such as the System for Operative Investigative Activities (SORM), which we assess may be integral in facilitating the actor’s current AiTM activity, judging from the large-scale nature of these operations.
This blog provides guidance on how organizations can protect against Secret Blizzard’s AiTM ApolloShadow campaign, including forcing or routing all traffic through an encrypted tunnel to a trusted network or using an alternative provider—such as a satellite-based connection—hosted within a country that does not control or influence the provider’s infrastructure. The blog also provides additional information on network defense, such as recommendations, indicators of compromise (IOCs), and detection details.
Secret Blizzard is attributed by the United States Cybersecurity and Infrastructure Agency (CISA) as Russian Federal Security Service (Center 16). Secret Blizzard further overlaps with threat actors tracked by other security vendors by names such as VENOMOUS BEAR, Uroburos, Snake, Blue Python, Turla, Wraith, ATG26, and Waterbug.
As part of our continuous monitoring, analysis, and reporting of the threat landscape, we are sharing our observations on Secret Blizzard’s latest activity to raise awareness of this actor’s tradecraft and educate organizations on how to harden their attack surface against this and similar activity. Although this activity poses a high risk to entities within Russia, the defense measures included in this blog are broadly applicable and can help organizations in any region reduce their risk from similar threats. Microsoft is also tracking other groups using similar techniques, including those documented by ESET in a previous publication.
AiTM and ApolloShadow deployment
In February 2025, Microsoft Threat Intelligence observed Secret Blizzard conducting a cyberespionage campaign against foreign embassies located in Moscow, Russia, using an AiTM position to deploy the ApolloShadow malware to maintain persistence and collect intelligence from diplomatic entities. An adversary-in-the-middle technique is when an adversary positions themself between two or more networks to support follow-on activity. The Secret Blizzard AiTM position is likely facilitated by lawful intercept and notably includes the installation of root certificates under the guise of Kaspersky Anti-Virus (AV). We assess this allows for TLS/SSL stripping from the Secret Blizzard AiTM position, rendering the majority of the target’s browsing in clear text including the delivery of certain tokens and credentials. Secret Blizzard has exhibited similar techniques in past cyberespionage campaigns to infect foreign ministries in Eastern Europe by tricking users to download a trojanized Flash installer from an AiTM position.
GreyNoise uncovers a stealth campaign exploiting ASUS routers, enabling persistent backdoor access via CVE-2023-39780 and unpatched techniques. Learn how attackers evade detection, how GreyNoise discovered it with AI-powered tooling, and what defenders need to know.
This activity was first discovered by GreyNoise on March 18, 2025. Public disclosure was deferred as we coordinated the findings with government and industry partners.
GreyNoise has identified an ongoing exploitation campaign in which attackers have gained unauthorized, persistent access to thousands of ASUS routers exposed to the internet. This appears to be part of a stealth operation to assemble a distributed network of backdoor devices — potentially laying the groundwork for a future botnet.
The tactics used in this campaign — stealthy initial access, use of built-in system features for persistence, and careful avoidance of detection — are consistent with those seen in advanced, long-term operations, including activity associated with advanced persistent threat (APT) actors and operational relay box (ORB) networks. While GreyNoise has made no attribution, the level of tradecraft suggests a well-resourced and highly capable adversary.
The attacker’s access survives both reboots and firmware updates, giving them durable control over affected devices. The attacker maintains long-term access without dropping malware or leaving obvious traces by chaining authentication bypasses, exploiting a known vulnerability, and abusing legitimate configuration features.
The activity was uncovered by Sift — GreyNoise’s proprietary AI-powered network payload analysis tool — in combination with fully emulated ASUS router profiles running in the GreyNoise Global Observation Grid. These tools enabled us to detect subtle exploitation attempts buried in global traffic and reconstruct the full attack sequence.
Read the full technical analysis.
Timeline of Events
March 17, 2025: GreyNoise’s proprietary AI technology, Sift, observes anomalous traffic.
March 18, 2025: GreyNoise researchers become aware of Sift report and begin investigating.
March 23, 2025: Disclosure deferred as we coordinated the findings with government and industry partners.
May 22, 2025: Sekoia announces compromise of ASUS routers as part of ‘ViciousTrap.’
May 28, 2025: GreyNoise publishes this blog.
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