Shellshock – what you need to know.

A post from Advent IM Consultant, Dale Penn

Shellshock what you need to know!


First of all what is the Shellshock software bug? Shellshock (sometimes known as Bashdoor) is a group of security vulnerabilities which were found in the Unix Bash Shell.

That can be pretty confusing for the average user so here is a small break down.

Unix is a term used to describe any operating system that uses among other things shell scripting and resembles the “Unix Philosophy” the most common of which are Apple’s OS X and Linux operating systems.

BASH - Shellshock

Apple….other fruits are available

Shell is a user interface to an operating systems services.

Bash Shell is the default shell on Linux and Apple’s OS X operating systems.


Bash is a shell that allows a user to input on Linux , Unix and Apple’s OS X operating systems. This can be achieved remotely using network protocols such as telnet and SSH which are protocols used to connect to remote servers in order to facilitate some sort of communications. Therefore this vulnerability can be exploited over a network!

Also this vulnerability requires no authorisation to exploit and could impact on the Confidentiality, integrity and availability of your information.

As such the US Department of Homeland Security have given Shellshock a 10 out of 10 in vulnerability severity (CVE-2014-6271 and CVE-2014-7169)

Chet Ramey a senior technology architect at Case Western Reserve University in Ohio, has been maintaining the Bash open source project and believes Shellshock has been present in Bash for around 22 years and is due to a new feature introduced in 1992.


Shellshock was announced on the 24 Sep 2014 and within hours there were reports of machines being compromised using the Shellshock vulnerability.  These compromised machines were used by hackers to create botnets. Botnets are a network of compromised computers that can be controlled remotely by the hacker. Hackers can then use the botnet to carry out attacks. The most common of which is a Directed Denial of Service (DDOS) attack where the attacker uses the members of his botnet to make a request of a specific target. The aim being to flood the target with so many requests that the target is then unable to function properly.

On 26 Sep 2014 a botnet named “wopbot”, which was created using the Shellshock vulnerabilities, was reported to have been used to carry out a DDOS attack against Akamai Technologies and to scan the United States Department of Defence!


Home/Office Computers

If you are using Microsoft home or office operating systems then you do not need to do anything as this vulnerability does not affect Microsoft.  However if you are running Unix, Linux or Apple’s OS X you need to download and apply the latest patches without delay! Patches have been made available by several suppliers to remediate this vulnerability.

Mobile Devices

It is not believed that iOS or android is vulnerable to the Shellshock attack however mobile devices can be vulnerable if you have customised your device (Jail broken your Apple device or use customised ROM’s on an android device). If you customised your device than you should consider carrying out the following: 

  • For an Jail broken apple device there is an updated version of Bash available on Cydia
  • If you are using customised ROM’s on your android device the XDA developers site has a link to an updated Bash shell (4.3.30)

Other Devices

Do not forget that many household items also connect to the internet I one form or another. It is important to keep these updated also to ensure your information the best protection. Instructions on how to carry this out will come with your product instruction manual and should be relatively straight forward.







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