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.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
The checkproc technique consists of comparing /proc with the
output of /bin/ps.
This technique is only available on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
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 on Linux 2.6 kernels.
Report unhide bugs on the bug tracker on sourceforge (http://sourceforge.net/projects/unhide/)
This manual page was written by Francois Marier francois@debian.org and Patrick Gouin. 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.