Detect Overwrite Process Arguments in Elastic Security
Adversaries may modify a process's in-memory arguments to change its name in order to appear as a legitimate or benign process. On Linux, the operating system stores command-line arguments in the process's stack and passes them to the main() function as the argv array. The first element, argv[0], typically contains the process name or path. By default, the Linux /proc filesystem uses this value to represent the process name. The /proc/<PID>/cmdline file reflects the contents of this memory, and tools like ps use it to display process information. During runtime, adversaries can erase the memory used by all command-line arguments for a process, overwriting each argument string with null bytes, then write a spoofed string into the memory region previously occupied by argv[0] to mimic a benign command. This technique is used by BPFDoor, which overwrites its argv[0] with names resembling Linux system daemons such as /sbin/udevd -d, dbus-daemon --system, and avahi-daemon: chroot helper.
MITRE ATT&CK
- Tactic
- Defense Evasion
- Technique
- T1036 Masquerading
- Sub-technique
- T1036.011 Overwrite Process Arguments
- Canonical reference
- https://attack.mitre.org/techniques/T1036/011/
Elastic Detection Query
sequence by host.name, process.pid
[process where event.type == "start" and
auditd.data.syscall == "execve" and
auditd.data.a0 != null and
process.executable != null and
auditd.data.a0 != process.executable and
(
auditd.data.a0 : ("/sbin/udevd*", "dbus-daemon*", "avahi-daemon*", "auditd*", "systemd-journald*", "/sbin/rpcbind*", "xinetd*", "crond*", "atd*", "acpid*", "smartd*", "irqbalance*") or
(not process.executable : ("/usr/*", "/bin/*", "/sbin/*", "/lib/*"))
)
]Detects T1036.011 process argument overwriting on Linux by comparing the value of argv[0] (auditd a0 field from EXECVE syscall) against the actual executable path from the exe field. Flags events where the claimed process name impersonates a known Linux system daemon or where the real executable resides outside standard system paths.
Data Sources
Required Tables
False Positives & Tuning
- Custom init wrappers or process supervisors (e.g., runit, s6) that legitimately rewrite argv[0] to reflect managed service names
- Python or Perl scripts that use setproctitle() to set a friendly display name distinct from the interpreter binary path
- Container entrypoint shims that rename themselves to match the wrapped process for observability purposes
Other platforms for T1036.011
Testing Methodology
Validate this detection against 3 adversary techniques from Atomic Red Team. Each test below lists the behaviour to exercise and the telemetry you should expect to see. Executable commands and cleanup steps are available with Pro.
- Test 1Overwrite argv[0] with Bash Process Substitution
Expected signal: Auditd EXECVE record with a0='/sbin/udevd -d' but exe pointing to /usr/bin/sleep (or /bin/sleep). The ps output shows the spoofed name. /proc/<PID>/cmdline shows '/sbin/udevd -d' while /proc/<PID>/exe symlinks to the actual sleep binary.
- Test 2Python prctl PR_SET_NAME Process Rename
Expected signal: Auditd SYSCALL record for prctl (syscall 157) with a0=15 (PR_SET_NAME) from python3. The /proc/<PID>/comm file will show 'avahi-daemon' while /proc/<PID>/exe still points to /usr/bin/python3. Process creation event shows python3 but ps output shows avahi-daemon.
- Test 3C Program argv[0] Overwrite and Fork (BPFDoor Simulation)
Expected signal: Auditd EXECVE record for /tmp/df00tech_argv_test. Fork SYSCALL (57) record. PROCTITLE record changing to hex-encoded '/sbin/udevd -d'. The child process shows PPID=1 (adopted by init) with args='/sbin/udevd -d' but /proc/<PID>/exe -> /tmp/df00tech_argv_test.
References (6)
- https://attack.mitre.org/techniques/T1036/011/
- https://sandflysecurity.com/blog/bpfdoor-an-evasive-linux-backdoor-technical-analysis/
- https://www.microsoft.com/en-us/security/blog/2022/05/19/rise-in-xorddos-a-deeper-look-at-the-stealthy-ddos-malware-targeting-linux-devices/
- https://man7.org/linux/man-pages/man2/prctl.2.html
- https://man7.org/linux/man-pages/man5/proc_pid_cmdline.5.html
- https://github.com/redcanaryco/atomic-red-team/blob/master/atomics/T1036.011/T1036.011.md
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