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Over the past year, FortiGuard Labs has been tracking a stealthy malware strain exploiting a range of vulnerabilities to infiltrate systems.  Initially disclosed by a Chinese cybersecurity firm under the name “Gayfemboy,” the malware resurfaced in July with new activity, targeting vulnerabilities in products from vendors such as DrayTek, TP-Link, Raisecom, and Cisco, and exhibiting signs of evolution in both form and behavior.  This Fortinet research presents an in-depth analysis of Gayfemboy, revealing its technical details and exploring the implications of its evolving behavior.[1]

Incidents - In July 2025, FortiGuard Labs observed a related payload exploiting multiple vulnerabilities. All instances traced back to a common attack source at 87[.]121[.]84[.]34 and a consistent download host at 220[.]158[.]234[.]135.
Figure 1: TP-Link Archer AX21 exploit traffic
Figure 2: Raisecom exploit traffic
Figure 3: DrayTek exploit traffic

Once analysts obtained the downloader scripts, they found a pattern for this download source, shown in the following table.

Figure 4: Raisecom downloader script

Fortinet infers that the downloader scripts are named after specific products—such as “asus,” “vivo,” “zyxel,” and “realtek”—because each script executes Gayfemboy using the corresponding product name as a parameter.

Figure 5: Asus downloader script

Figure 6: Vivo downloader script

Figure 7: Zyxel downloader script

Figure 8: Realtek downloader script

The Gayfemboy campaign spans multiple countries, including Brazil, Mexico, the United States, Germany, France, Switzerland, Israel, and Vietnam.  Its targets also cover a broad range of sectors, such as Manufacturing, Technology, Construction, and Media or Communications.

Figure 9: Gayfemboy affected countries

Malware Analysis - Gayfemboy employs its first layer of obfuscation during the file download stage. Unlike Mirai and Gafgyt variants, which typically use Linux architecture names as file extensions, Gayfemboy assigns distinct names to each architecture, avoiding predictable naming conventions.
 

The following analysis focuses on the “xale1” variant, which targets the x86-64 Linux architecture.

Using the DiE (Detect It Easy) tool, analysts determined that Gayfemboy is packed using UPX.  However, the malware modifies the standard UPX header “UPX!,” replacing it with a non-printable string represented by the hexadecimal value “10 F0 00 00” to evade detection.

Figure 10: Anti-unpacking via a modified UPX magic header

Upon execution, the malware displays the string “twinks :3.”

Figure 11: Pop-up string after execution

Gayfemboy then scans each subdirectory under /proc/[PID]/, inspecting the path of every corresponding /proc/[PID]/exe to gather information on running processes and their executable locations.

Figure 12: Scan process subdirectories

Next, it inspects each /proc/[PID]/exe path for telltale keywords—e.g., (deleted), /tmp/., /bot., dvrlocker, /.ai, and /.*—that are commonly associated with other malware.  If any match is found, Gayfemboy immediately terminates the corresponding process to remove competing infections.
Figure 13: Keywords commonly associated with other malware

Gayfemboy includes four primary functions: Monitor, Watchdog, Attacker, and Killer.  The Monitor function tracks threads and processes while incorporating basic anti-analysis techniques.  It loads 47 command strings into memory and scans all /proc/[PID]/cmdline entries. If a match is found, the malware immediately terminates the associated process.
 

Figure 14: A monitor function that kills specific processes

Within the Monitor function, Gayfemboy includes two dedicated sub-functions: Self-Persistence and Sandbox Evasion. 

Self-persistence ensures the malware remains active.  If Gayfemboy detects that its process has been terminated, it automatically re-executes itself.

Figure 15: Self-persistence in the monitor function

As part of its Sandbox Evasion technique, Gayfemboy introduces a deliberate 50-nanosecond delay.  

If executed in a sandbox environment that cannot accurately handle such a fine-grained delay, the timing function fails, causing the malware to misinterpret the result and initiate a fallback sleep of approximately 27 hours.

Figure 16: Sandbox evasion in the monitor function

The Watchdog function begins by attempting to bind to a specific UDP port—47272. If the bind fails, it assumes another instance of the Watchdog is already running.  In that case, Gayfemboy connects to 127.0.0.1:47272 and sends a packet containing the formatted string <[timestamp]|[PID]>.  If this message is sent more than nine times without receiving a response, the malware concludes it is unresponsive or compromised and terminates itself.
Figure 17: Watchdog function

The Attacker function is responsible for launching DDoS attacks and enabling backdoor access.  It preloads several attack methods into memory for on-demand use, including: UDP flood, UDP bypass, TCP flood, TCP SYN flood, ICMP flood, Heartbeat, and a Backdoor module.

Figure 18: UDP flood attack

Gayfemboy uses the string “meowmeow” as a trigger to activate its backdoor functionality.

Figure 19: Backdoor method

If Gayfemboy has not yet established a connection with its command-and-control (C2) server, it initiates communication by randomly selecting a predefined C2 domain from a list.  To resolve these domains, the malware uses public DNS servers—such as 1.1.1.1, 8.8.8.8, or 8.8.4.4—instead of relying on the system’s configured resolver.

This technique helps bypass local DNS filtering or sinkholing, making it more difficult for defenders to block C2 communication through static IP blacklists.  By dynamically resolving domain names through public resolvers, Gayfemboy can rotate its C2 infrastructure more flexibly and maintain persistence even if one or more domains are taken down.

The known C2 domains include:

• cross-compiling[.]org
• i-kiss-boys[.]com
• furry-femboys[.]top
• twinkfinder[.]nl
• 3gipcam[.]com

Figure 20: Resolved C2 server domain

Figure 21: Resolved C2 server domain traffic

Once a C2 domain is successfully resolved, Gayfemboy attempts to establish communication by scanning a predefined list of 15 ports.  It systematically checks whether each port is open and can be used for C2 traffic, increasing its chances of successful connection even in environments with restrictive outbound filtering.
 

Once connected, the C2 server can issue various commands to the infected host.  If the received packet is exactly four bytes long, it corresponds to one of four predefined commands, each identified by a specific hexadecimal sequence:
 

These commands enable basic control, persistence, and reconnaissance functionality with minimal overhead—likely designed to keep communication lightweight and harder to detect.

Figure 22: Four-byte-length command from the C2 server

If a command packet from the C2 server exceeds five bytes, Gayfemboy parses the message differently.  It first extracts the two-byte length field, then interprets the remaining data based on a command format where:

The first byte is the main command ID, and

The second byte is the sub-command.

The malware then executes the appropriate behavior depending on the command type:
 

This structure enables the attacker to issue more complex commands, remotely manage the bot, evade defenses, and dynamically control the attack behavior.

Figure 23: Loading an attack method
Figure 24: Triggering a UDP flood attack

The Killer function enforces self-protection through two mechanisms:

Time Check – It monitors the system clock and triggers self-termination if it detects a near 24-hour discrepancy, which may indicate sandbox manipulation or attempted system rollback.

Remote Kill Command – It listens for a C2-issued command containing the string ^kill^. Upon receiving it, the malware terminates itself immediately.

Conclusion - While Gayfemboy inherits structural elements from Mirai, it introduces notable modifications that enhance both its complexity and ability to evade detection. This evolution reflects the increasing sophistication of modern malware, reinforcing the need for proactive, intelligence-driven defense strategies.  Staying ahead requires not only regular patching but also in-depth analysis and exposure of emerging threats to develop effective countermeasures and mitigate risk.

IOCs

Hosts

141[.]11[.]62[.]222
149[.]50[.]96[.]114
220[.]158[.]234[.]135
78[.]31[.]250[.]15
5[.]182[.]206[.]7
5[.]182[.]204[.]251
cross-compiling[.]org
i-kiss-boys[.]com
furry-femboys[.]top
twinkfinder[.]nl
3gipcam[.]com

Files

Downloader

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9f77b86621c7cec885ab89a3dcf0548a7ee17c8c88f66780dfc7dcb2a13da146

Gayfemboy

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1b6deb5f47ebfe3a0cbb35751f3df6a893c6570cb7863c74e4262397edd6552e

This article is shared with permission at no charge for educational and informational purposes only.

Red Sky Alliance is a Cyber Threat Analysis and Intelligence Service organization.  We provide indicators of compromise information via a notification service (RedXray) or an analysis service (CTAC).  For questions, comments, or assistance, please contact the office directly at 1-844-492-7225 or feedback@redskyalliance.com    

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[1] https://www.fortinet.com/blog/threat-research/iot-malware-gayfemboy-mirai-based-botnet-campaign/