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APT 41: Threat Intelligence Report and Malware Analysis

Medium
Published: Tue Jun 10 2025 (06/10/2025, 10:52:57 UTC)
Source: AlienVault OTX General

Description

APT41, a sophisticated Chinese state-sponsored threat actor, blends cyber espionage with cybercrime tactics. They target various sectors globally, including healthcare, telecom, and government entities. Recently, APT41 was observed using Google Calendar for malware command-and-control on a Taiwanese government website. Their attack chain involves spear-phishing emails, malicious ZIP archives, and a three-module malware system called ToughProgress. This malware uses stealthy techniques like in-memory execution, encryption, and process hollowing to evade detection. The unique aspect of ToughProgress is its use of Google Calendar events for covert data exchange, creating a stealthy communication channel for remote command execution and data exfiltration.

AI-Powered Analysis

AILast updated: 07/10/2025, 11:31:18 UTC

Technical Analysis

APT41 is a sophisticated Chinese state-sponsored threat actor known for blending cyber espionage with financially motivated cybercrime tactics. This group targets a wide range of sectors globally, including healthcare, telecommunications, and government entities, leveraging advanced and stealthy malware to achieve their objectives. The recent activity highlighted involves the use of a novel malware family called ToughProgress, which employs a multi-stage attack chain beginning with spear-phishing emails containing malicious ZIP archives. Upon successful infection, ToughProgress operates through a three-module system that uses advanced evasion techniques such as in-memory execution to avoid writing payloads to disk, encryption to protect its communications and payloads, and process hollowing to masquerade as legitimate processes, thereby evading detection by traditional security tools. A particularly unique and innovative aspect of this malware is its use of Google Calendar events as a covert command-and-control (C2) channel. By embedding commands and exfiltrated data within calendar events, the malware establishes a stealthy and resilient communication method that blends into normal network traffic, making detection and disruption more challenging. This technique allows the attacker to remotely execute commands and exfiltrate sensitive data without raising typical network security alarms. The attack was notably observed targeting a Taiwanese government website, indicating a focus on high-value geopolitical targets. The tactics, techniques, and procedures (TTPs) employed by APT41 include spear-phishing (T1566.001), use of living-off-the-land binaries (T1218.011), process hollowing (T1055.012), and covert channel communications (T1102.003), among others, demonstrating a high level of operational sophistication and adaptability. Although no known exploits in the wild have been reported for this specific malware, the threat actor’s history and capabilities suggest a persistent and evolving risk to targeted organizations.

Potential Impact

For European organizations, the presence of APT41 and its ToughProgress malware poses significant risks, particularly to sectors such as healthcare, telecommunications, and government agencies that are often targeted for espionage and intellectual property theft. The use of spear-phishing as an initial infection vector means that employees are at risk of being tricked into opening malicious attachments, potentially leading to widespread compromise. The stealthy nature of the malware, including in-memory execution and process hollowing, complicates detection and remediation efforts, increasing the likelihood of prolonged undetected presence within networks. The innovative use of Google Calendar for command-and-control communications can bypass traditional network monitoring tools, making it difficult for security teams to identify malicious traffic. This could lead to unauthorized data exfiltration, loss of sensitive information, disruption of critical services, and damage to organizational reputation. Additionally, the targeting of government entities suggests potential risks to national security and critical infrastructure within Europe. The medium severity rating reflects the complexity of the attack and the moderate ease of exploitation, but the potential impact on confidentiality and integrity is substantial, especially if sensitive or classified information is compromised.

Mitigation Recommendations

European organizations should implement targeted and advanced defensive measures beyond standard cybersecurity hygiene. These include: 1) Enhancing email security by deploying advanced anti-phishing solutions that use machine learning to detect spear-phishing attempts and malicious attachments, combined with user awareness training focused on recognizing sophisticated phishing campaigns. 2) Deploying endpoint detection and response (EDR) solutions capable of detecting in-memory execution, process hollowing, and anomalous process behavior to identify and contain ToughProgress malware early. 3) Monitoring and analyzing network traffic for unusual use of legitimate services such as Google Calendar, including inspecting calendar event metadata and frequency patterns that deviate from normal organizational use. 4) Implementing strict application whitelisting and restricting the use of living-off-the-land binaries to reduce the attack surface exploited by APT41. 5) Conducting regular threat hunting exercises focused on indicators of compromise related to APT41’s TTPs and maintaining updated threat intelligence feeds to stay informed about emerging variants. 6) Enforcing multi-factor authentication (MFA) across all remote access points to reduce the risk of credential compromise. 7) Establishing incident response plans that specifically address advanced persistent threats and covert communication channels to ensure rapid containment and remediation.

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Technical Details

Author
AlienVault
Tlp
white
References
["https://www.resecurity.com/blog/article/apt-41-threat-intelligence-report-and-malware-analysis"]
Adversary
APT41
Pulse Id
68480e89dbe1f2bc0746a80c
Threat Score
null

Indicators of Compromise

Hash

ValueDescriptionCopy
hash1ca609e207edb211c8b9566ef35043b6
MD5 of 50124174a4ac0d65bf8b6fd66f538829d1589edc73aa7cf36502e57aa5513360
hash2ec4eeeabb8f6c2970dcbffdcdbd60e3
MD5 of 151257e9dfda476cdafd9983266ad3255104d72a66f9265caa8417a5fe1df5d7
hash65da1a9026cf171a5a7779bc5ee45fb1
MD5 of 3b88b3efbdc86383ee9738c92026b8931ce1c13cd75cd1cda2fa302791c2c4fb
hash876fb1b0275a653c4210aaf01c2698ec
MD5 of 469b534bec827be03c0823e72e7b4da0b84f53199040705da203986ef154406a
hasha04cff8208769ecdc43e14291273c3a540199d07
SHA1 of 469b534bec827be03c0823e72e7b4da0b84f53199040705da203986ef154406a
hasha6a29946269107b9fd3bcd85386ef9d7438b7ae1
SHA1 of 3b88b3efbdc86383ee9738c92026b8931ce1c13cd75cd1cda2fa302791c2c4fb
hashdf5ba7ca764063d60eb4dc49d9251c11928b8024
SHA1 of 50124174a4ac0d65bf8b6fd66f538829d1589edc73aa7cf36502e57aa5513360
hashe7ad8d1d670757eba247d4992af54a9003e35a7d
SHA1 of 151257e9dfda476cdafd9983266ad3255104d72a66f9265caa8417a5fe1df5d7
hash151257e9dfda476cdafd9983266ad3255104d72a66f9265caa8417a5fe1df5d7
hash3b88b3efbdc86383ee9738c92026b8931ce1c13cd75cd1cda2fa302791c2c4fb
hash469b534bec827be03c0823e72e7b4da0b84f53199040705da203986ef154406a
hash50124174a4ac0d65bf8b6fd66f538829d1589edc73aa7cf36502e57aa5513360

Domain

ValueDescriptionCopy
domaincloud.msapp.workers.dev
domainpubs.infinityfreeapp.com
domainresource.infinityfreeapp.com
domainword.msapp.workers.dev
domainterm-restore-satisfied-hence.trycloudflare.com
domainways-sms-pmc-shareholders.trycloudflare.com

Threat ID: 684811df17e89880603e42e2

Added to database: 6/10/2025, 11:07:11 AM

Last enriched: 7/10/2025, 11:31:18 AM

Last updated: 7/30/2025, 4:15:25 PM

Views: 24

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