A major vulnerability in the bash shell was recently discovered
called ShellShock. This vulnerability
affects the systems that have not updated bash and the one that provide web
hosting in any form. For example WordPress hosting, which allows the remote
attackers to execute arbitrary commands, upload files, send infected emails
etc.
ShellShock
vulnerability got a score of 10/10 which means you must pay attention to it as soon
as possible as it allows the attacker to gain a shell on the infected system.
Additionally, if the bug is exploited over CGI, then the situation will become
even worse. So, it is highly recommended to resolve this issue before it is too
late.
How
to verify if you are infected with ShellShock?
Follow the steps and run each line after $, if you find
the word “vulnerable” then you are infected.
- hobbes@metal:~$ export badvar='() { :;}; echo vulnerable’
- hobbes@metal:~$ bash -c “echo I am an innocent sub process in ‘$BASH_VERSION'”
- vulnerable
- I am an innocent sub process in 4.3.22(1)-release
Once a system becomes vulnerable to ShellShock bash vulnerability it allows the attacker to do any malicious
activity including modifying content of the web server, spoils the appearance
of the website, change codes, steal user data from databases, change passwords,
and many more.
Shell scripting is mostly used in Linux which means there
are multiple ways for the vulnerability to be triggered. Red Hat which is one
of the most famous companies that provides Linux said “Because of the pervasive
use of the Bash shell, this issue is quite serious and should be treated as
such.”
What
to do once you became a victim?
If you are an administrator of Linux server, update your
version of bash as soon as possible. However, if you are using Ubuntu,
executing ‘apt-get update’ and then ‘apt-get upgrade’ will remove ShellShock bash bug from the server.
Tips
to minimize the damage:
- Keep your system patched.
- Remove unnecessary software’s that are not used.
- Use software with auto updation capability.
- Keep identifying which systems are infected
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Nice tips to be secured from ShellShock, as such bugs are not easily identified and thus cause much loss. Quiet an informative post.
ReplyDeleteYeah that really true that Shellshock bug attacks the system. To ensure weather it has effect my system or not i have verified and yes my system was effected by it but by taking the tips suggested in the blog. I have minimize the risk.
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