Attacks/Breaches

9/14/2007
02:40 AM
Connect Directly
Google+
Twitter
RSS
E-Mail
50%
50%

How to Bypass the IDS/IPS

'Simple Nomad' shows how bad guys can wage targeted attacks by probing, fingerprinting IDSes and IPSes

If you think all IDS/IPS signatures are created equal, think again.

The quality of an IDS or IPS signature may be what stands between you and a targeted attack, says researcher Simple Nomad, a.k.a. Mark Loveless, who will demonstrate gaping holes he's found in IDS and IPS products next week at IT Security World in San Francisco.

"A lot of people say the whole model of IDS/IPS is broken," says Loveless, who will present his latest research on bypassing IDS and IPS systems. "But the problem here boils down to poor signature-writing in some instances... Good signature-writing is effective."

One big problem is some signatures for filtering exploits are written to the publicly disclosed exploit, rather than the underlying vulnerability, he says. So if a known exploit's payload code is 4,096 bytes, for instance, the IDS or IPS signature would "look" for that characteristic to filter out the exploit. But a clever attacker could merely alter the size of the exploit's payload to, say, 5,000 bytes to avoid detection by the IDS or IPS.

"That happens a lot -- signature-writers write against the exploit as opposed to the vulnerability," Loveless says, and since most vendors outsource at least some, if not all, of their IDS/IPS signatures, this can provide attackers an easy way in.

Loveless, senior security architect for Vernier Networks, which makes a network access control (NAC) product that does intrusion prevention with a combination of signatures and anomaly detection, says part of his job is to check the quality of signatures that Vernier outsources. "Most of the time they come in fine, but sometimes a vendor will send five signatures and I may have to write an additional three signatures to provide the proper coverage, as well as edit their five signatures."

IDS/IPS evasion research isn't new -- Metasploit creator HD Moore demonstrated at Black Hat USA 2006 some application-level exploits that zip right past an IPS. (See IDS/IPS: Too Many Holes?)

Loveless' research, meanwhile, focuses more on how attackers can use weaknesses in signatures as well as how they can case, or scan, the perimeter to detect which brand of IDS or IPS is sitting on the victim's network, and then use that intelligence to wage the ultimate attack.

In the first wave -- reconnaissance -- the attacker can determine whether the device is an IPS versus an IDS if he can access "XYZ" before a first-stage attack, but not afterward, Loveless says. Delays in blocking the attack may be a clue that an admin is reading his IDS logs -- thus it's an IDS.

Loveless says he will demonstrate how an attacker can then manually "fingerprint" the brand of IDS or IPS, and then adjust the attack to take advantage of that product's weaknesses. "If you have some idea of what brand of IPS covers this vulnerability or that one, you can fingerprint it and say this looks like Brand X or Brand Y."

Fingerprinting specific products is more difficult for an attacker to do than probing the perimeter to determine if it's an IDS or IPS, however, he says.

But even the most airtight of IDSes or IPSes won't stop a determined attacker. "Ideally, every probe that came in, [the IDS or IPS] would block," Loveless says. "But then that tells the attacker he shouldn't go through the network... Instead he should try the WAP [wireless access point]."

Have a comment on this story? Please click "Discuss" below. If you'd like to contact Dark Reading's editors directly, send us a message.

  • Vernier Networks Inc.

    Kelly Jackson Higgins is Executive Editor at DarkReading.com. She is an award-winning veteran technology and business journalist with more than two decades of experience in reporting and editing for various publications, including Network Computing, Secure Enterprise ... View Full Bio

    Comment  | 
    Print  | 
    More Insights
  • Comments
    Newest First  |  Oldest First  |  Threaded View
    1.9 Billion Data Records Exposed in First Half of 2017
    Kelly Jackson Higgins, Executive Editor at Dark Reading,  9/20/2017
    Get Serious about IoT Security
    Derek Manky, Global Security Strategist, Fortinet,  9/20/2017
    Register for Dark Reading Newsletters
    White Papers
    Video
    Cartoon Contest
    Write a Caption, Win a Starbucks Card! Click Here
    Latest Comment: This comment is waiting for review by our moderators.
    Current Issue
    Security Vulnerabilities: The Next Wave
    Just when you thought it was safe, researchers have unveiled a new round of IT security flaws. Is your enterprise ready?
    Flash Poll
    [Strategic Security Report] How Enterprises Are Attacking the IT Security Problem
    [Strategic Security Report] How Enterprises Are Attacking the IT Security Problem
    Enterprises are spending more of their IT budgets on cybersecurity technology. How do your organization's security plans and strategies compare to what others are doing? Here's an in-depth look.
    Twitter Feed
    Dark Reading - Bug Report
    Bug Report
    Enterprise Vulnerabilities
    From DHS/US-CERT's National Vulnerability Database
    CVE-2017-0290
    Published: 2017-05-09
    NScript in mpengine in Microsoft Malware Protection Engine with Engine Version before 1.1.13704.0, as used in Windows Defender and other products, allows remote attackers to execute arbitrary code or cause a denial of service (type confusion and application crash) via crafted JavaScript code within ...

    CVE-2016-10369
    Published: 2017-05-08
    unixsocket.c in lxterminal through 0.3.0 insecurely uses /tmp for a socket file, allowing a local user to cause a denial of service (preventing terminal launch), or possibly have other impact (bypassing terminal access control).

    CVE-2016-8202
    Published: 2017-05-08
    A privilege escalation vulnerability in Brocade Fibre Channel SAN products running Brocade Fabric OS (FOS) releases earlier than v7.4.1d and v8.0.1b could allow an authenticated attacker to elevate the privileges of user accounts accessing the system via command line interface. With affected version...

    CVE-2016-8209
    Published: 2017-05-08
    Improper checks for unusual or exceptional conditions in Brocade NetIron 05.8.00 and later releases up to and including 06.1.00, when the Management Module is continuously scanned on port 22, may allow attackers to cause a denial of service (crash and reload) of the management module.

    CVE-2017-0890
    Published: 2017-05-08
    Nextcloud Server before 11.0.3 is vulnerable to an inadequate escaping leading to a XSS vulnerability in the search module. To be exploitable a user has to write or paste malicious content into the search dialogue.