UNHIDE(8) System Manager's Manual UNHIDE(8)
NAME
unhide — forensic tool to find hidden processes
SYNOPSIS
unhide [OPTIONS] TEST_LIST
unhide-posix proc | sys
DESCRIPTION
unhide is a forensic tool to find processes hidden by rootkits, Linux
kernel modules or by other techniques. It detects hidden processes us-
ing six techniques.
OPTIONS
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 un-
hideGui).
-H Provide a slightly human frienlier output. This option adds end-
ing messages to tests and indicates when no hidden process is
found.
TEST_LIST
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).
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 -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.
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 gath-
ered 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 func-
tion.
This technique is only available with version unhide-linux.
The checkRRgetinterval technique consists of comparing information gath-
ered 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 posi-
tives.
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.
EXAMPLES
Quicker test:
unhide quick
Quick test:
unhide quick reverse
Standard test:
unhide sys proc
Deeper test:
unhide -m -d sys procall brute reverse
BUGS
Report unhide bugs on the bug tracker on GitHub (https://github.com/YJe-
sus/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.
SEE ALSO
unhide-tcp (8).
AUTHOR
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.
LICENSE
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/li-
censes/gpl.html>.
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
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