UNHIDE(8)

💅 UNHIDE — the forensic tea ☕ (section 8, system manager's manual, bestie)

okay so picture this: something on your box is being sneaky. like, a process that's there but doesn't want you to see it. that's the whole vibe of unhide, and honestly? iconic. this is a forensic tool to find processes hidden by rootkits, Linux kernel modules or by other techniques. it catches them using six techniques 🕵️♀️✨

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🌸 SYNOPSIS 🌸

unhide [OPTIONS] TEST_LIST
unhide-posix proc | sys

that's it. that's the whole summoning ritual. 💫

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✨ DESCRIPTION ✨

unhide is a forensic tool to find processes hidden by rootkits, Linux kernel modules or by other techniques. periodt. it detects those hidden processes using six techniques — and she is thorough, bestie. 🦋

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🎀 OPTIONS 🎀

heads up bestie: these options are only available for unhide-linux, not for unhide-posix. no cap. 🙈

• -d — do a double check in brute test to avoid false positive. extra credit energy.
• -f — write a log file (unhide-linux.log) in the current directory. receipts!! 🧾
• -h — display help. when in doubt, ask her. 💁♀️
• -m — do more checks. as of 2012-03-17 version, this option has only effect for the procfs, procall, checkopendir and checkchdir tests. also: implies -v. she's nosy and she knows it.
• -r — use the alternate version of sysinfo check</> in standard tests.
• -V — show version and exit. bye bestie 👋
• -v — be verbose, display warning message (default : don't display). this option may be repeated more than once — stack it, queen. 🗣️
• -u — do unbuffered write to stdout. this option could be useful when unhide is spawned by another process (e.g. it's used by unhideGui). very "i'm being observed" of her.
• -H — provide a slightly more human frienlier output. this option adds ending messages to tests and indicates when no hidden process is found. she's being nice about it 🫶

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🦋 TEST_LIST 🦋

so the checks you're gonna run = one or more of the following tests. and the standard tests are basically an aggregation of one or more elementary test(s). it's giving "choose your fighter". ✨

🌈 Standard tests

the brute technique consists of bruteforcing the all process IDs. this technique is only available with version unhide-linux.

the proc technique consists of comparing /proc with the output of /bin/ps.

the procall technique combinates proc and procfs tests. this technique is only available with version unhide-linux.

the procfs technique consists of comparing information gathered from /bin/ps with information gathered by walking in the procfs. with the -m option, this test makes more checks, see checkchdir test. this technique is only available with version unhide-linux.

the quick technique combines the proc, procfs and sys techniques in a quick way. it's about 20 times faster but may give more false positives. this technique is only available with version unhide-linux. fast and messy, a true icon 💅

the reverse technique consists of verifying that all threads seen by ps are also seen in procfs and by system calls. it is intended to verify that a rootkit has not killed a security tool (IDS or other) and make ps showing a fake process instead. this technique is only available with version unhide-linux.

the sys technique consists of comparing information gathered from /bin/ps with information gathered from system calls.

🧚 Elementary tests

the checkbrute technique consists of bruteforcing the all process IDs. this technique is only available with version unhide-linux.

the checkchdir technique consists of comparing information gathered from /bin/ps with information gathered by making chdir() in the procfs. with the -m option, it also verify that the thread appears in its "leader process" threads list. this technique is only available with version unhide-linux.

the checkgetaffinity technique consists of comparing information gathered from /bin/ps with the result of call to the sched_getaffinity() system function. this technique is only available with version unhide-linux.

the checkgetparam technique consists of comparing information gathered from /bin/ps with the result of call to the sched_getparam() system function. this technique is only available with version unhide-linux.

the checkgetpgid technique consists of comparing information gathered from /bin/ps with the result of call to the getpgid() system function. this technique is only available with version unhide-linux.

the checkgetprio technique consists of comparing information gathered from /bin/ps with the result of call to the getpriority() system function. this technique is only available with version unhide-linux.

the checkRRgetinterval technique consists of comparing information gathered from /bin/ps with the result of call to the sched_rr_get_interval() system function. this technique is only available with version unhide-linux.

the checkgetsched technique consists of comparing information gathered from /bin/ps with the result of call to the sched_getscheduler() system function. this technique is only available with version unhide-linux.

the checkgetsid technique consists of comparing information gathered from /bin/ps with the result of call to the getsid() system function. this technique is only available with version unhide-linux.

the checkkill technique consists of comparing information gathered from /bin/ps with the result of call to the kill() system function. Note : no process is really killed by this test. phew. nobody's getting hurt here, she's just asking. 🫶 this technique is only available with version unhide-linux.

the checknoprocps technique consists of comparing the result of the call to each of the system functions. no comparison is done against /proc or the output of ps. this technique is only available with version unhide-linux.

the checkopendir technique consists of comparing information gathered from /bin/ps with information gathered by making opendir() in the procfs. this technique is only available with version unhide-linux.

the checkproc technique consists of comparing /proc with the output of /bin/ps. this technique is only available with version unhide-linux.

the checkquick technique combines the proc, procfs and sys techniques in a quick way. it's about 20 times faster but may give more false positives. this technique is only available with version unhide-linux.

the checkreaddir technique consists of comparing information gathered from /bin/ps with information gathered by making readdir() in /proc and /proc/pid/task. this technique is only available with version unhide-linux.

the checkreverse technique consists of verifying that all threads seen by ps are also seen in procfs and by system calls. it is intended to verify that a rootkit has not killed a security tool (IDS or other) and make ps showing a fake process instead. this technique is only available with version unhide-linux.

the checksysinfo technique consists of comparing the number of process seen by /bin/ps with information obtained from sysinfo() system call. this technique is only available with version unhide-linux.

the checksysinfo2 technique is an alternate version of checksysinfo test. it might (or not) work better on kernel patched for RT, preempt or latency and with kernel that don't use the standard scheduler. it's also invoked by standard tests when using the -r option. this technique is only available with version unhide-linux.

⭐ Exit status:

• 0 — if OK,
• 1 — if a hidden or fake thread is found. 🚨

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🔥 EXAMPLES 🔥

Quicker test:

unhide quick

Quick test:

unhide quick reverse

Standard test:

unhide sys proc

Deeper test:

unhide -m -d sys procall brute reverse

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💀 BUGS 💀

report unhide bugs on the bug tracker on GitHub (https://github.com/YJesus/Unhide/issues) — she wants the feedback, bestie, fr fr.

with recent versions of Linux kernel (> 2.6.33), the sysinfo test may report false positives. it may be due to optimization in the scheduler, the use of cgroup or even the use of systemd. the use of the PREEMPT-RT patch amplifies the occurrence of the problem. this is currently under investigation. not her fault, she's literally investigating. 🔍😭

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👑 SEE ALSO 👑

• unhide-tcp (8).

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💖 AUTHOR 💖

this manual page was written by Francois Marier (francois@debian.org) and Patrick Gouin (patrickg.github@free.fr). legends, honestly.

permission is granted to copy, distribute and/or modify this document under the terms of the GNU General Public License, Version 3 or any later version published by the Free Software Foundation.

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🌈 LICENSE 🌈

license GPLv3+: GNU GPL version 3 or later http://gnu.org/licenses/gpl.html. this is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. periodt. no take-backs. 💅

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and that's the whole page, bestie 🫶 this one lives under the Administration commands umbrella and it's dated May 2024 — go forth and catch those sneaky little processes. slay. ✨👑🦋