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How a new PlugX variant abuses DLL search order hijacking

Medium
Published: Thu Sep 25 2025 (09/25/2025, 19:15:17 UTC)
Source: AlienVault OTX General

Description

A new campaign targeting telecommunications and manufacturing sectors in Central and South Asian countries has been discovered, delivering a new variant of PlugX. The campaign, active since 2022, shows overlaps between RainyDay and Turian backdoors, including the abuse of legitimate applications for DLL sideloading and shared encryption methods. The new PlugX variant's configuration format resembles that of RainyDay, suggesting attribution to Naikon. Analysis of victimology and technical implementation indicates a potential connection between Naikon and BackdoorDiplomacy, possibly sourcing tools from the same vendor. The malware families use similar infection chains, loaders, and shellcode structures, with shared RC4 keys for payload decryption. This campaign highlights the evolving tactics of Chinese-speaking threat actors and the potential collaboration between previously distinct groups.

AI-Powered Analysis

AILast updated: 09/25/2025, 19:26:59 UTC

Technical Analysis

The analyzed threat involves a newly identified variant of the PlugX malware family, actively deployed since 2022 in targeted campaigns against telecommunications and manufacturing sectors primarily in Central and South Asia. This variant leverages DLL search order hijacking, a technique where malicious DLLs are loaded by abusing the order in which Windows searches for DLLs, allowing attackers to execute arbitrary code under the guise of legitimate applications. The campaign exhibits overlaps with other malware families such as RainyDay and Turian, sharing infection chains, loaders, shellcode structures, and even encryption keys (notably RC4 keys) for payload decryption. The configuration format of this PlugX variant closely resembles that of RainyDay, suggesting a common origin or shared development resources, attributed to the Naikon threat actor group. Furthermore, analysis indicates a potential operational link between Naikon and BackdoorDiplomacy, possibly indicating collaboration or shared tooling from a common vendor. The campaign’s tactics reflect an evolution in Chinese-speaking threat actors’ methodologies, combining DLL sideloading with sophisticated backdoor deployment to maintain persistence and evade detection. The use of legitimate applications for DLL sideloading complicates detection efforts, as it blends malicious activity with normal system processes. The campaign employs multiple MITRE ATT&CK techniques, including DLL search order hijacking (T1574.001), code injection (T1055), credential dumping (T1003), and lateral movement (T1021.002), underscoring a multi-faceted attack chain designed for stealth and persistence. While no known exploits in the wild are reported, the campaign’s longevity and complexity highlight a mature threat actor infrastructure.

Potential Impact

For European organizations, particularly those in telecommunications and manufacturing sectors, this threat poses significant risks. If the malware were to spread or be adapted to target European entities, it could lead to unauthorized access, data exfiltration, espionage, and disruption of critical infrastructure operations. The abuse of DLL search order hijacking complicates detection and mitigation, potentially allowing attackers to maintain long-term persistence within networks. Given the shared encryption keys and modular payloads, attackers could customize the malware to evade existing defenses. The compromise of telecommunications infrastructure could impact data confidentiality and availability, affecting communication services vital for business and government operations. Manufacturing sector infections could disrupt production lines, leading to financial losses and supply chain interruptions. Additionally, the potential link between Naikon and BackdoorDiplomacy suggests a broader espionage campaign that could target sensitive governmental or industrial information within Europe. Although the campaign is currently focused on Central and South Asia, the tactics and malware families involved have global relevance and could be repurposed against European targets, especially given geopolitical tensions and the strategic importance of these sectors.

Mitigation Recommendations

European organizations should implement targeted defenses against DLL search order hijacking by enforcing strict application whitelisting and employing tools that monitor and validate DLL loads, such as Microsoft’s Sysinternals Process Monitor and Application Control policies. Regularly auditing and restricting the execution of unsigned or suspicious DLLs can reduce risk. Network segmentation and strict access controls should be enforced to limit lateral movement opportunities. Endpoint Detection and Response (EDR) solutions should be tuned to detect behaviors indicative of code injection, shellcode execution, and unusual process spawning associated with PlugX and related malware. Organizations should also deploy threat hunting activities focused on indicators of compromise related to RainyDay, Turian, and PlugX, including monitoring for shared RC4 key usage patterns. Multi-factor authentication (MFA) and credential hygiene are critical to prevent credential dumping and reuse. Given the malware’s use of legitimate applications for sideloading, maintaining an up-to-date inventory of authorized software and monitoring for anomalous DLL loads is essential. Incident response plans should include procedures for isolating infected systems and eradicating persistent backdoors. Collaboration with national cybersecurity agencies and sharing threat intelligence related to these malware families can enhance collective defense.

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Technical Details

Author
AlienVault
Tlp
white
References
["https://github.com/Cisco-Talos/IOCs/blob/main/2025/09/how-rainyday-turian-and-a-new-plugx-variant-abuse-dll-search-order-hijacking.txt","https://blog.talosintelligence.com/how-rainyday-turian-and-a-new-plugx-variant-abuse-dll-search-order-hijacking/"]
Adversary
null
Pulse Id
68d594c5084d2279312e988e
Threat Score
null

Indicators of Compromise

Hash

ValueDescriptionCopy
hash1644f0fc35546b1863a314a090b37cfd
hash37df2da57f726aa5e044963610ac66ab
hash421320ccf8972de50f8574a5b1c8d308
hash4828bbea12517a16c4790e30b10570ea
hash4ed171a64cae819b224aa3e2bc844219
hash547caf34217c17358783c5ab48681f9f
hash637525e6eaeabd2998dc10c14a67e940
hash7104f3dd3738b04df0bc6993045f3b21
hash84649f22ccde1dad34016117a7b296e5
hash982659f15f45efcd699d26069f7e3e05
hashaa4e5f8a00e4ab5af551c7e1f53da2ff
hashbfb0255751fcff41670d97520d4354fb
hashde5baeb185484e99c83b46988a6002a4
hashe819778c1655f65582bf3f426f112b72
hashf3ac847b3465cba107c947a7f72f5aa2
hashf6930322bf6cb1b85a61126ccf17a2b9
hashfd9e7d100cdf72d6f8e93e0c04d764a1
hash040328541d1c8c29fb11d5ca6ad2efd1593b00f2
hash071581b2092f8eec9e3fe3bec10c44284d191f93
hash282353f2a49b02a6aa89140d5a4fa13a1340119f
hash388627cd6b66a7714af6c6d416ac6a5ff6690cf1
hash4e08a2615d13bc21be04b6c2d4ce20798f2b1f04
hash58efa253735c5fff7d24fb705f7b63d986208518
hash606b1c3bb432e50ef6ee94bdfbcca4ce5cf9617d
hash764f44e6673bf073264ddf6ec09ef1db7e9bdedb
hash84e5e85926145461e1eca6e698336df27b9bf63a
hasha10583689711c4de8667a7300d0e8f0c7bcb78a3
hasha95943205d4296f9a393c5dbc110f532393487ba
hashbc7bf6fd94afd80116ae4d004c273883049a867a
hashbd45ab53d77d0252b5b0934e5ac90319243908d0
hashbf211e08d0c327c67c4e658d0bca26ac6c308f4d
hashc068b3700b81e5b11194ba6f976e2a5731522598
hashc35d55de271a3ff3222bb46f5d27039e0a8e24a0
hashd258d0102834c47e133002b212d5ea12ed4bac20
hashd2fffbe63b70a5993cb6fb035a2f665c7fa92a75
hashd91337af047c8b4f26e40ce8187910daf2d19a7d
hash00dbc8a4b3121af5a19504a9d969e36e709556420a6117eb3533f1d2a8100fd9
hash03cec3b010853893310fea486ecfddf09642a7a5c695c70db77d22bc7c402234
hash0443289b1fc556c5ef4bbfa13774500e3936d965799a9c27be0601170601094d
hash0bc51a290919c52cc62b3d8b4eed96609edf264f742d0409c975553b0cdc84a8
hash0ec83d1deb6065cac8ba8f849cdf5672da7313ec2e860a7d71bb7e397e661394
hash10479191f2e06ff11797fc4dda2e38ae6667c9dc396fac32a6cf76965358ade6
hash1357b4577bd2d99546df2ef5cb4cd3bcbe2a9ee91783eb6798fc7dea660bc5e5
hash262df5a17003b3dc06d6eb2fff89eb66709819df8219f2842bfc913be9f85c10
hash2755de59ef87f9f38c236ed860a1f6f41a1d864126f54c4c0a7f87d4b4f63b20
hash2cc9959ff1172366e71c8ed89be5cb23f17abce1125871fe47a9465f59e6ed17
hash3480613294bc1e1704616dbf5628b92d7186246b87dbef1c8c3dbae13fe35c8b
hash419eabb1c4c9be3ebdd726c73c497dcd2e39245f7e72ffcb67e032fcefe5ba13
hash42c9505c2c55b80e0e311cd6da6a5263b946c8ae8bd8162b0280a1e9be7f174b
hash4c2253777f1b6e54431c28a7a284577bda3464aa82837bbd7de57a00869f0c5b
hash6a7880e14b9f03fe281c28b93094b7b150a1360cbf64dd0b47c87e111db406ca
hash7b028a9bd2bc0c306ab6561cf702406f5925fc073f9d0d2d9408ceccd6907743
hash906ff72d4ea9cd831c58dc009fb1bbe407e8f430208a63d3dffd3f8e1da73f6e
hasha12ed375965859d9434c9f651eef2f3663bb076963fec31723176c9083117671
hasha92ed5f831c99bb84208ef7d7c733e0183a79de40f9d3b3be54744951f0a1391
hashab526d5ed335860ac2fe0adee26de1a95a3c528299800ddbb4d1e2dd91267252
hashaec2d0cbd2f195bf35e55019a29f0d6109451eb85dc7941b73e3b562b065a11c
hashb03fe49036c3830f149135068ff54f5c6c6622008a6fcb7edbf6b352e9a0acc0
hashb1ee96026a3fc0ee55dab3b73896e88760f909b3c52d4a0152288d90e63f2e63
hashb691b2c1846ea75bb5b07a21c8664ecdb6379685623ba45fe6ca552e94a58ebc
hashc91595edd1c9a0a2c1168e3bfa532e4a7dbb6b1380afd80ba445b728622798a4
hashc922ef32c4ab94f8b870c62883f3e41755ec705db76ec4efb0d343458f1e28c7
hashdef64a0564f33f39235e3778d86863565a40493ae1f5c075552611d79383b471
hashdff0164392e12d2bbb85c630419fd349f9d87f80bdb92774c0b53d7e063e77e4
hashe29767ffb75be9f363a39ba9b66785ecfc992e3d91ec9fc46515ef94c37dc0b6
hashf0397688418692c467488ac37d362b9b1efdba8b60b0d99725e2b66f3e03badb
hashf0ad27f8737ac1a079a52c91d8b5cdd554cd42dccc597de8337e0c25d5287dd2
hashf3abb0cc802f3d7b95fc8762b94bdcb13bf39634c40c357301c4aa1d67a256fb
hashfd6b1ca0f26e54fa9c97ea15c834e58ffb71798df38071ad00b14f19d6a4126c
hashfd87149d6b8fdcad5d84ba4a3ca52e1cef8f0c54cafca6dbbb5d156f313d79dd
hashfe4f88bdfff87a94bd57bc16c20d199ee548e551b4aca852bcc013d0955d7ce8

Ip

ValueDescriptionCopy
ip103.136.45.108
ip103.172.10.165
ip103.9.14.218
ip117.239.199.202
ip117.254.105.200
ip123.181.24.36
ip138.112.25.25
ip141.164.59.111
ip23.254.225.184
ip36.75.75.75
ip45.114.192.137
ip66.42.62.253
ip71.162.181.51

Domain

ValueDescriptionCopy
domain2fgithub.com
domainnewsinfom.org
domainasp.asphspes.com
domainmailserver.kozow.com
domainpay.googleinstall.com

Threat ID: 68d5977082abd4e860dbde52

Added to database: 9/25/2025, 7:26:40 PM

Last enriched: 9/25/2025, 7:26:59 PM

Last updated: 9/26/2025, 7:41:06 AM

Views: 10

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