unhide — forensic tool to find hidden processes

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

       Report unhide bugs on the bug tracker on GitHub (https://github.com/YJesus/Unhide/issues)
       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.

unhide  is  a  forensic  tool  to  find  processes  hidden  by rootkits, Linux kernel modules or by other
       techniques.  It detects hidden processes using six techniques.

       Quicker test:
              unhide quick

       Quick test:
              unhide quick reverse

       Standard test:
              unhide sys proc

       Deeper test:
              unhide -m -d sys procall brute reverse

       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.

Administration commands                             May 2024                                           UNHIDE(8)

       unhide — forensic tool to find hidden processes

       Options are only available for unhide-linux not for unhide-posix.

       -d     Do a double check in brute test to avoid false positive.

       -f     Write a log file (unhide-linux.log) in the current directory.

       -h     Display help

       -m     Do more checks. As of 2012-03-17 version, this option has only effect  for  the  procfs,  procall,
              checkopendir and checkchdir tests.
              Implies -v

       -r     Use alternate version of sysinfo check in standard tests

       -V     Show version and exit

       -v     Be  verbose,  display warning message (default : don't display).  This option may be repeated more
              than once.

       -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).

       -H     Provide  a  slightly  human  frienlier  output.   This  option  adds  ending messages to tests and
              indicates when no hidden process is found.

       unhide-tcp (8).

unhide [OPTIONS] TEST_LISTunhide-posixproc|sys

       The checks to do consist of one or more of the following tests.
       The standard tests are the aggregation of one or more elementary test(s).

       Standardtests:

       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 -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.

       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.

       Elementarytests:

       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.
       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.

   Exitstatus:
       0      if OK,

       1      if a hidden or fake thread is found.