Developers have been scrambling to patch a newly discovered vulnerability in Bash, a widely used piece of code that interprets user commands for a computer. Bash has existed for 25 years and is utilized by the hundreds of millions of computers worldwide running Unix, Linux and Mac OS X operating systems. The flaw allows hackers to access a device and slip in malicious code, taking over the computer. The hacker can make the device or server do just about anything from becoming part of a botnet to stealing customer account information. Banks' core systems and servers often run on Linux or Unix, as do certain closed-circuit cameras and ATMs. Banks' IT administrators will need to scan all systems and vendors for the vulnerability and install patches.