Posts Tagged: UNIX

Sep 14

‘Shellshock’ Bug Spells Trouble for Web Security

As if consumers weren’t already suffering from breach fatigue: Experts warn that attackers are exploiting a critical, newly-disclosed security vulnerability present in countless networks and Web sites that rely on Unix and Linux operating systems. Experts say the flaw, dubbed “Shellshock,” is so intertwined with the modern Internet that it could prove challenging to fix, and in the short run is likely to put millions of networks and countless consumer records at risk of compromise.

The bug is being compared to the recent Heartbleed vulnerability because of its ubiquity and sheer potential for causing havoc on Internet-connected systems — particularly Web sites. Worse yet, experts say the official patch for the security hole is incomplete and could still let attackers seize control over vulnerable systems.

The problem resides with a weakness in the GNU Bourne Again Shell (Bash), the text-based, command-line utility on multiple Linux and Unix operating systems. Researchers discovered that if Bash is set up to be the default command line utility on these systems, it opens those systems up to specially crafted remote attacks via a range of network tools that rely on it to execute scripts, from telnet and secure shell (SSH) sessions to Web requests.

According to several security firms, attackers are already probing systems for the weakness, and that at least two computer worms are actively exploiting the flaw to install malware. Jaime Blasco, labs director at AlienVault, has been running a honeypot on the vulnerability since yesterday to emulate a vulnerable system.

“With the honeypot, we found several machines trying to exploit the Bash vulnerability,” Blasco said. “The majority of them are only probing to check if systems are vulnerable. On the other hand, we found two worms that are actively exploiting the vulnerability and installing a piece of malware on the system. This malware turns the systems into bots that connect to a C&C server where the attackers can send commands, and we have seen the main purpose of the bots is to perform distributed denial of service attacks.”

The vulnerability does not impact Microsoft Windows users, but there are patches available for Linux and Unix systems. In addition, Mac users are likely vulnerable, although there is no official patch for this flaw from Apple yet. I’ll update this post if we see any patches from Apple.

Update, Sept. 29 9:06 p.m. ET: Apple has released an update for this bug, available for OS X Mavericks, Mountain Lion, and Lion.

The U.S.-CERT’s advisory includes a simple command line script that Mac users can run to test for the vulnerability. To check your system from a command line, type or cut and paste this text:

env x='() { :;}; echo vulnerable' bash -c "echo this is a test"

If the system is vulnerable, the output will be:

 this is a test

An unaffected (or patched) system will output:

 bash: warning: x: ignoring function definition attempt
 bash: error importing function definition for `x'
 this is a test

US-CERT has a list of operating systems that are vulnerable. Red Hat and several other Linux distributions have released fixes for the bug, but according to US-CERT the patch has an issue that prevents it from fully addressing the problem. Continue reading →

Jul 12

How to Break Into Security, Grossman Edition

I recently began publishing a series of advice columns for people who are interested in learning more about security as a craft or profession. For the third installment in this series, I interviewed Jeremiah Grossman, chief technology officer of WhiteHat Security, a Web application security firm.

A frequent speaker on a broad range of security topics, Grossman stressed the importance of coding, networking, and getting your hands dirty (in a clean way, of course).

BK: How did you get started in computer security?

Grossman: For me it was…I could hack stuff and I did it in my spare time and someone offered me a job — which was Yahoo. But before that, I was just a UNIX admin. I was thinking about this question a lot, and what occurred to me is that I don’t know too many people in infosec who chose infosec as a career. Most of the people who I know in this field didn’t go to college to be infosec pros, it just kind of happened. They followed opportunity.

BK: You might have seen that the last two experts I asked had somewhat different opinions on this question, but how important is it that someone interested in this field know how to code?

Grossman: It’s tough to give solid advice without knowing more about a person. For instance, are they interested in network security or application security? You can get by in IDS and firewall world and system patching without knowing any code; it’s fairly automated stuff from the product side. But with application security, it is absolutely mandatory that you know how to code and that you know software. So with Cisco gear, it’s much different from the work you do with Adobe software security. Infosec is a really big space, and you’re going to have to pick your niche, because no one is going to be able to bridge those gaps, at least effectively.

BK: So would you say hands-on experience is more important that formal security education and certifications?

Grossman: The question is are people being hired into entry level security positions straight out of school? I think somewhat, but that’s probably still pretty rare. There’s hardly anyone coming out of school with just computer security degrees. There are some, but we’re probably talking in the hundreds. I think the universities are just now within the last 3-5 years getting masters in computer security sciences off the ground. But there are not a lot of students in them.

BK:  What do you think is the most important qualification to be successful in the security space, regardless of a person’s background and experience level?

Grossman: The ones who can code almost always [fare] better. Infosec is about scalability, and application security is about scalability. And if you can understand code, you have a better likelihood of being able to understand how to scale your solution. On the defense side, we’re out-manned and outgunned constantly. It’s “us” versus “them,” and I don’t know how many of “them,” there are, but there’s going to be too few of “us “at all times.  So whatever your solution is or design criteria, you’re going to have to scale it. For instance, you can imagine Facebook…I’m not sure many security people they have, but…it’s going to be a tiny fraction of a percent of their user base, so they’re going to have to figure out how to scale their solutions so they can protect all those users.

Continue reading →