Misconceptions of Linux Security | TechSNAP 155

Misconceptions of Linux Security | TechSNAP 155

We explore some common misconceptions about Linux security. Plus the 0-Day hitting Microsoft Office users…

A great big batch of your questions, our answers, and much much more!

On this week’s episode, of TechSNAP.

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— Show Notes: —

Exploring the misconceptions of Linux Security

  • “There is a perception out there that Linux systems don\’t need additional security”
  • As Linux grows more and more mainstream, attacks become more prominent
  • We have already seen malware with variants targeting Linux desktop users, Flash and Java exploits with Linux payloads
  • Linux servers have been under attack for more than a decade, but these incidents are rarely publicized
  • The most common attacks are not 0day exploits against the kernel or some critical service, but compromised web applications, or plain old brute force password cracking
  • However, it is still important to keep services up to date as well (openssh, openssl, web server, mail server, etc)
  • Typical ‘best practice’ involves having firewalls, web application firewalls and intrusion detection systems. These systems cannot prevent every type of attack.
  • Firewalls generally do not help attacks against web applications, because they operate at layer 3 & 4 and can no detect an attempted exploit
  • Web Application Firewalls operate at layer 7 and inspect HTTP traffic before it is sent to the application and attempt to detect exploit or SQL injection attempts. These are limited by definitions of what is an attack, and are also often limited to providing protection for specific applications, since protecting an application generally means knows exactly what legitimate traffic will look like
  • Intrusion detection systems again rely on detecting specific patterns and are often unable to detect an attack, or detect so many false positives that the attack is buried in a report full of noise and isn’t recognized
  • Linux backdoors have become remarkably sophisticated, taking active steps to avoid detection, including falling silent when an administrator logs in, and suspending exfiltration when an interface is placed in promiscuous mode (such as when tcpdump is run)
  • Linux servers are often out of date, because most distributions do not have something similar to Microsoft’s “Patch Tuesday”. Security updates are often available more frequently, but the irregular cadence can cause operational issues. Most enterprise patch management systems do not include support for Linux, and it is often hard to tell if a Linux server is properly patched
  • “The main problem is that these system administrators think their [Linux] systems are so secure, when they haven\’t actually done anything to secure them,” David Jacoby, a senior security researcher for the Global Research and Analysis Team at Kaspersky Lab said. For example, the default Linux configuration for most distributions does not restrict login attempts, Jacoby warned. Attackers can attempt to brute-force passwords by running through a list of possibilities without having to worry about locking out the account or getting disconnected from the server. This is something the administrator has to configure manually, and many don\’t, Jacoby said.

0day exploit in MS Word triggered by Outlook preview

  • Microsoft issued a warning on Monday of a new 0day exploit against MS Word being exploited in the wild
  • Microsoft has released an emergency Fix-It Solution until a proper patch can be released
  • This attack is especially bad since it doesn’t not require the victim to open the malicious email, looking at the message in Outlook’s preview mode will trigger the exploit
  • According to Microsoft’s advisory the flaw is also present in Word 2003, 2007, 2010, 2013, Word Viewer and Office for Mac 2011
  • The attack uses a malicious RTF (Rich-Text file), Outlook renders RTF files with MS Word by default
  • The Fix-It solution disables automatically opening emails with RTF content with MS Word
  • This attack can also be worked around by configuring your email client to view all emails in plain-text only
  • Instructions for Office 2003, 2007 and 2010
  • Instructions for Outlook 2013
  • “The attack is very sophisticated, making use of an ASLR bypass, ROP techniques (bypassing the NX bit and DEP), shellcode, and several layers of tools designed to detect and defeat analysis”
  • The code attempts to determine if it is running in a sandbox and will fail to execute, to hamper analysis and reverse engineering
  • The exploit also checks how recently windows updates have been installed on the machine. “The shellcode will not perform any additional malicious action if there are updates installed after April, 8 2014”
  • Additional Coverage – ThreatPost


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