Posts Tagged ‘cracker’

How to keep track of All User accounts executed commands, highest CPU consumers and user times on Linux

Tuesday, February 5th, 2013

Reading Time: 5minutes

Linux accounting keeping an eye on all user run commands time accounting find cpu eaters

For people interested into statistics of how Linux existing users are spending, there log in times and what kind of commands each of users is executing, take a look at acct
acct is existing on all mainstream Linux distributions is a great sysadmin tool. acct is a great tool whether you have a system where a multitude of users you don't trust has to be monitored. It is an absolutely must have for anyone willing to run, lets say  experimental honeypot or  free shell host. acct is useful for paranoid sysadmins who like to always knows what there users are running as well as in situation where some of users is suspected to be a potential cracker trying to root the host.

Below is description of acct package on Debian:

# apt-cache show acct| grep -i description -A 8
Description: The GNU Accounting utilities for process and login accounting
 GNU Accounting Utilities is a set of utilities which reports and summarizes
 data about user connect times and process execution statistics.
 .
 "Login accounting" provides summaries of system resource usage based on connect
 time, and "process accounting" provides summaries based on the commands
 executed on the system.
 .
 The 'last' command is provided by the sysvinit package and not included here.

To start using acct, just install it with usual:

# apt-get install --yes acct

(Whether on Debian / Ubuntu Linux);

On Fedora, CentOS and RHEL and other RPM based Linuxes issue;

yum --y install psacct

On deb based Linux distributions, whether acct collects statistics is controlled via:

/etc/default/acct

# cat /etc/default/acct
# Defaults for acct

# If you want to keep acct installed, but not started automatically, set this
# variable to 0. Because /etc/cron.daily/acct calls the initscript daily, it is
# not sufficient to stop acct once after booting if your machine remains up.
ACCT_ENABLE="1"

# Amount of days that the logs are kept.
ACCT_LOGGING="30"

After installed to start collecting user "process accounting" data run acct via init script;

# /etc/init.d/acct start
Turning on process accounting, file set to '/var/log/account/pacct'.
Done..

The file gathering info on system usage, CPU load, user ran commands /var/log/account/psacct is a binary and unreadable tailing it with tail -f .

On CentOS / Fedora Linux to Enable acct account statistics gathering in future boot and from present moment on do;

# chkconfig psacct on
# /etc/init.d/psacct start

1. Find out all commands executed by Linux user account (lastcomm)

Once user accounting is running to get information of every command ever executed on user shell use lastcomm cmd. For example:

# lastcomm hipo

bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.03 secs Tue Feb  5 00:20
sed                    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
uname                  hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
dircolors              hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
uname                  hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.03 secs Tue Feb  5 00:20
sed                    hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
uname                  hipo     pts/1      0.00 secs Tue Feb  5 00:20
bash              F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
id                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
mesg                   hipo     pts/1      0.00 secs Tue Feb  5 00:20
verse                  hipo     pts/1      0.00 secs Tue Feb  5 00:20
cowrand                hipo     pts/1      0.00 secs Tue Feb  5 00:20
cowsay                 hipo     pts/1      0.03 secs Tue Feb  5 00:20
cowrand           F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
head                   hipo     pts/1      0.00 secs Tue Feb  5 00:20
tail                   hipo     pts/1      0.00 secs Tue Feb  5 00:20
head                   hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
cowrand           F    hipo     pts/1      0.00 secs Tue Feb  5 00:20
awk                    hipo     pts/1      0.00 secs Tue Feb  5 00:20
wc                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20

A lot of the initial commands shown to run on pts/1 is not actual commands, by the user but are just stuff run on user login time via /etc/bash.bashrc, /etc/profile, ~/.bashrc. ~/.bash_profile.

lastcomm displayed output from 2nd column is a special flag giving more information on how and for what purpose command was executed. In above output
F
– indicates the command run after a fork.
X – is returned if a command exit with SIGTERM (kill signal)
D – in case of generated command core dump (D is good one to look for whether checking a suspicious user profile, as it is so common exploits use core dumping to get root superuser access)
S – means the command is run with superuser privileges (this one you will see usually whether inspecting user profile of a cracker who run exploit using core dump – a lot of Ds followed by some shell code to run as superuser)

2. Get statistics on CPU use time of services (daemons) and user accounts

psacct is very handy, whether you have CPU server overloads and you have difficulty finding out what are the "CPU hungry processes". To get those use summarized accounting information tool;

# sa -m
                                     2619      31.06re       0.54cp         0avio      2907k
root                                 2448      30.19re       0.52cp         0avio      2817k
www-data                               33       0.06re       0.02cp         0avio      3687k
hipo                                   72       0.15re       0.01cp         0avio      6217k
qscand                                 11       0.36re       0.00cp         0avio      5326k
vpopmail                               48       0.25re       0.00cp         0avio      1486k
qmails                                  6       0.00re       0.00cp         0avio       968k
sshd                                    1       0.04re       0.00cp         0avio     12632k

-m (prints user summary).

3. Find all system users running certain commands

Another good use of lastcomm command is to grep over all users executed command for precise commands of interest. One very good use case is if you catch a system abuser running certain exploit or DoS tool on the host and you want to make sure no-one else on the system doesn't try running it.

# lastcomm ls
ls                     www-data __         0.00 secs Tue Feb  5 00:40
ls                     www-data __         0.00 secs Tue Feb  5 00:30
ls                     hipo     pts/7      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     hipo     pts/1      0.00 secs Tue Feb  5 00:20
ls                     www-data __         0.00 secs Tue Feb  5 00:20
ls                     root     pts/0      0.00 secs Tue Feb  5 00:10
ls                     root     pts/0      0.00 secs Tue Feb  5 00:10
ls                     www-data __         0.00 secs Tue Feb  5 00:10
 

4. Get statistics of most active system users in hours

There is one tool called ac, which is similar in what it does to last command, just like last it uses /var/log/wtmp binary log file to get its user login times stats . The difference is ac provides more and better structured user login time length info.

Its very useful if you want to have idea, which user spends most time connected to host.

$ ac -p
    sic                                  4.86
    hipo                                 4.80
    root                                25.80
    play                                 0.02

To get general info on how much overall hours all existing users spend doing stuff on node;

$ ac total 35.61

To know which days from the month users were most active:

$ ac -d
Feb 1 total 14.54
Feb 2 total 0.97
Feb 3 total 12.47
Feb 4 total 5.96
Today total 1.73

Install grsecurity kernel security from binary package (without kernel recompile) on Debian and Ubuntu

Monday, July 26th, 2010

Reading Time: 2minutes
GRsecurity is since long time known that it is a next generation armouring agains 0 day local kernel exploits as well as variousof other cracker attacks.
Grsecurity is an innovative approach to security utilizing a multi-layered detection, prevention, and containment model. It is licensed under the GNU GPL.
GRSecurity is linux kernel patch which has to be applied to the kernel before compile time. However we’ve been lucky and somebody has taken the time and care to prepare linux image binary deb packagesfor Debian and Ubuntu .

Some of the key grsecurity features are :

  • An intelligent and robust Role-Based Access Control (RBAC) system that can generate least privilege policies for your entire system with no configuration
  • Change root (chroot) hardening
  • /tmp race prevention
  • Prevention of arbitrary code execution, regardless of the technique used (stack smashing, heap corruption, etc)
  • Prevention of arbitrary code execution in the kernel
  • Reduction of the risk of sensitive information being leaked by arbitrary-read kernel bugs
  • A restriction that allows a user to only view his/her processes
  • Security alerts and audits that contain the IP address of the person causing the alert

To install from the http://debian.cr0.org/ grsecurity patched kernel image repository use the following steps:

1. Include in your /etc/apt/sources.list

deb http://ubuntu.cr0.org/repo/ kernel-security/
deb http://debian.cr0.org/repo/ kernel-security/

Directly from the bash command line execute:

debian:~# echo "deb http://ubuntu.cr0.org/repo/ kernel-security/" >> /etc/apt/sources.list
debian:~# echo "deb http://debian.cr0.org/repo/ kernel-security/" >> /etc/apt/sources.list

2. Add the debian.cr0.org repository gpg key to the trusted repositories key ring

Download the repository’s gpg key , check it (it has been signed with the repository owner GPG key )

Thence from to include the gpg key to the trusted repos key issue:

debian:~# apt-key add kernel-security.asc

3. Install the linux-image-grsec package itself

Currently to install on my x86_amd64 Debian Squeeze/Sid and possibly on Debian Lenny I’ve issued:


debian:~# apt-get update
debian:~# apt-get install linux-image-2.6.32.15-1-grsec

Now simply restarting your system and choosing the Linux kernel patched with the GRsecurity kernel patch from Grub should enable you to start using the grsecurity patched kernel.
Though this tutorial is targetting Debian it’s very likely that the grsecurity hardened kernel installation on Debian will be analogous.

World Fastest Md5 cracker

Saturday, March 14th, 2009

Reading Time: < 1minute
A friend of mine (SIC-a) referred me to a great article on the topic of password cracking.It seems some guy out there has created a md5 password cracker which is claimed to be the world’slargest password cracker. The article could be seen here Enjoy!The idea behind the cracker is that it takes advantage of the Video card (GPU) or in other words the video CPU.It’s reported to work with NVidia 8xxx++ and a couple of others :)END—–