Posts Tagged ‘Perl’

Installation and Configuration of Clamav antivirus on Debian GNU / Linux

Monday, September 9th, 2013

Clamav logo installing Clamav antivirus to scan periodically Debian server websites for viruses

Clamav Antivirus is one of must have packages installed on a new Debian Linux server. It is not only necessary whether configuring a new Mail server be it Qmail or Postfix but is good to have to always check files on a Webserver. Until few years infecting of Sites with Viruses / Installing WebShells or Backdooring for further access using Perl or PHP vulnerable PHP code was not so common, However nowadays with increase of complexity of languages and increase of not security minded programmers this possibility dramatically increaed. Thus nowadays, whether I configure a new Apache + PHP + CGI support server I always install Clamav AV. Some might argue that Clamav Virus definitions are still too little compared to proprietary solutions like BitDefender / AVG or Avast but since my experience with this under Linux is not so bright as well as Clamav captures essential Viruses and Backdoors I still prefer to keep on with Clamav.  Even on home Desktops with Linux clamav is of use as there are plenty of free-ware software for Linux which come only distributed only in a binary form and hence its good to check them with clamav before use whether they don't contain some well known Rootkit or Virus. Over the years Clamav has done great job for me whether I had to clean up "hacked" hosts containing  script kiddie exploit scanners or Virus infected ELF binaries
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1. Installing ClamAV in Debian Wheezy Linux

Before time there was a separate Debian repository called Volatille providing latest version release of Clamav, since Debian Squeeze Volatille project is discontinued, thus installing on Wheezy as a deb package is only available via standard Debian repositories.

apt-get update && apt-get --yes upgrade
...

apt-get install --yes clamav clamav-daemon

As package dependencies you get installed:

clamav clamav-base clamav-freshclam libbz2-1.0 libclamav1 libcurl3 libidn11 ucf

Clamav-Daemon will launch immediately after packages are installed and is available as process name /usr/sbin/clamd

# ps ax |grep -i clam
 2641 ?        Ssl    6:39 /usr/sbin/clamd
 2791 ?        Ss    12:04 /usr/bin/freshclam -d --quiet
12300 pts/0    S+     0:00 grep -i clam

2. Updating Clamav Antivirus Definitions

Its worthy say few words on clamav-freshclam as it is part of ClamAV which is used to update Clamav Virus definitions. Update of ClamAV vir definitions are updating automatically through /usr/bin/freshclam daemon which is started automatically by Debian postconfiguration scripts right after Clamav install.

Manual update of AV definitions can be done also with freshclam.

# freshclam
ClamAV update process started at Sun Sep  8 17:48:36 2013
main.cvd is up to date (version: 54, sigs: 1044387, f-level: 60, builder: sven)
daily.cvd is up to date (version: 17830, sigs: 1696886, f-level: 63, builder: neo)
bytecode.cld is up to date (version: 225, sigs: 42, f-level: 63, builder: dgoddard)


To keep an eye on definition auto-updates (useful to check where something fails), check out in /var/log/clamav/freshclam.log

A sure indication that Anvirus updates are conducting fine should be log records like:
 

Sun Sep  8 16:27:44 2013 -> ————————————–
Sun Sep  8 17:27:44 2013 -> Received signal: wake up
Sun Sep  8 17:27:44 2013 -> ClamAV update process started at Sun Sep  8 17:27:44 2013
Sun Sep  8 17:27:44 2013 -> main.cvd is up to date (version: 54, sigs: 1044387, f-level: 60, builder: sven)
Sun Sep  8 17:27:44 2013 -> daily.cld is up to date (version: 17830, sigs: 1696886, f-level: 63, builder: neo)
Sun Sep  8 17:27:44 2013 -> bytecode.cld is up to date (version: 225, sigs: 42, f-level: 63, builder: dgoddard)
Sun Sep  8 17:27:47 2013 -> ————————————–



3. Configuring ClamAV

For Desktop use clamav default config is pretty good. However for servers its good to raise  2 up MaxThreads:

By default MaxThreads is 12

MaxThreads 12

Change to from 30 to 80 depending on how powerful machine ClamAV runs, even on some servers more Clamav threads might be necessary

MaxThreads 30

Other value I like changing is SelfCheck 3600 is too long time for clamav Virus definitions integrity I prefer to set it to 600, i.e.

SelfCheck 600

By default ClamAV is also configured to scan archive files as well. However for this to work you will have to have previously installed unzip and unrar on system. If still you don't have them installed run:

# apt-get install --yes unrar unzip
...

Note that you will need to have non-free part of Debian deb repositories to /etc/apt/sources.list

Here is one of my sources.list
 

deb http://ftp.uk.debian.org/debian squeeze main contrib non-free
deb http://security.debian.org/ squeeze/updates main contrib non-free
deb-src http://security.debian.org/ squeeze/updates main contrib non-free

deb http://ftp.debian.skynet.be/ftp/debian/ squeeze main contrib non-free
deb-src http://ftp.debian.skynet.be/ftp/debian/ stable main contrib non-free

deb http://security.debian.org squeeze/updates main contrib non-free
deb-src http://security.debian.org/ squeeze/updates main contrib non-free

3. Scanning with ClamAV

# clamscan -r /tmp/
./dos-58.160.208.43: OK
./dos-108.18.38.140: OK
./dos-188.194.80.100: OK
./dos-91.224.160.135: OK
./dos-128.253.117.70: OK
./dos-128.172.143.110: OK
./dos-77.92.102.34: OK
./dos-195.230.5.12: OK
...

....
----------- SCAN SUMMARY -----------
Known viruses: 2735887
Engine version: 0.97.8
Scanned directories: 1
Scanned files: 129
Infected files: 0
Data scanned: 0.00 MB
Data read: 0.00 MB (ratio 0.00:1)
Time: 4.769 sec (0 m 4 s)


-r flag stands for recursive scan – e.g. scan all sub-directories in directory and its content

To not flood your console / ssh connection one very useful option is -i (print only whetherinfected files are matched). Here is one more sample case:

# clamscan -r -i /var/tmp/
----------- SCAN SUMMARY -----------
Known viruses: 2735887
Engine version: 0.97.8
Scanned directories: 1
Scanned files: 2
Infected files: 0
Data scanned: 0.26 MB
Data read: 0.13 MB (ratio 1.97:1)
Time: 4.824 sec (0 m 4 s)


Whether you're on a physical server console and it has pc speaker or sound blaster use –bell option to ring a bell every time a Virus infection is found, for exmpl.

# clamscan -r -i --bell /var/www/

4. Scanning periodically and reporting with ClamAV directories with websites

A very common use of ClamAV is to just setup a scheduled cronjob once a month to scan, whether server folder containing a bunch of websites in separate Virtualhosts contain some viruses or malicious stuff. Then as administrator check those logs once a month to make sure server site or group of sites does not become banned in search engine (blocked by Google Chrome and Firefox as Virus hotbed) …
# crontab -u root -e
00 02 01 * * clamscan -r /var/www -l /var/log/websites-scan.log

Then once a month check out /var/log/websites-scan.log

Linux: Delete empty lines from text file with sed, awk, grep and vim

Saturday, March 23rd, 2013

As a system administrator, sometimes is necessary to do basic plain text processing for various sysadmin tasks. One very common task I do to remove empty lines in file. There are plenty of ways to do it i.e. – with grep, sed, awk, bash, perl etc.

1. Deleting empty file lines with sed

The most standard way to do it is with sed, as sed was written to do in shell quick regexp. Here is how;

sed '/^\s*$/d' file_with_empty_lines.txt > output_no_empty_lines.txt

2. Deleting empty file lines with awk

It is less of writting with awk, but I always forget the syntax and thus I like more sed, anyways here is how with awk;

cat file_with_empty_lines.txt | awk 'NF' >
output_no_empty_lines.txt

3. Deleting empty lines with grep

Grep  regular expression can be used. Here is grep cmd to cut off empty lines from file;

grep -v '^\s*$' file_with_empty_lines.txt >
output_no_empty_lines.txt

4. Delete empty files with vi / vim text editor

Open vi / vim text editor

$ vim

Press Esc+: and if empty lines doesn't have empty space characters use command

g/^$/d

Whether, empty lines contain " " – space characters (which are not visible in most text editors), use vi cmd:
g/^ $/d

Graphical representation of Open Source history generated from SVN and GIT commits with Gource – Software version control visualization

Thursday, September 1st, 2011

A friend of mine has sent me a link to awesome videos produced with an open source tool called Gource

The tool is really awesome as its capable of producing amazing graphical visualizations from source tree repositories obtained from software SVN or GIT repositories

Someone used it to create a wonderful videos and relate the graphical visualization with wondeful music to show graphically the Software development for the main Free Software Projects. 😉

The points which move around in videos are graphical representation of the repository source, the nodes which buzzle around are users who commit source in the project repositories.
The whole graphical representation is being generated based on all the latest source hold inside the software repository, on top of the videos its visible the date of each of the source commits.
Below are few of the nice videos, the rest are available for checkout in Youtube, Enjoy! 😉

OpenOffice Development – Graphical representation

PHP Development – Graphical representation

History of Python development since 1990 with Gource

Development of MySQL 2000-2010 – Graphical representation

Perl development history in less then 4 minutes. Visualized with gource.