nullcon 2010 - Signature based Malware Detection PoC for Websites

Proof-Of-Concept: Signature Based Malware Detection for Websites and Domain Administrators - Anant Kochhar

Malware /`mæl.weə(ɹ)/
Software developed for the purpose of causing harm to a computer system and its users.
Back Door, Key Logger, Botnet Zombie

Know them, “Trust” them

Drive-By Downloads AKA IFRAME and Script Injections

First Wave: Mass SQL Injection
First noticed in late 2007.
Tool based.
Identified vulnerable pages across the internet using search engines.
Sprayed them with SQL injection payloads-
Inserted script injections indiscriminately in all database columns
Infected data was reflected in dynamic pages

Payload Source: http://www.f-secure.com/weblog/archives/00001427.html

Affected Page With Rubbish Data

Source: http://www.scmagazineus.com/mass-sql-injection-attack-compromises-70000-websites/article/100497/ Source: http://www.scmagazineus.com/sql-attack-hits-125000-sites/article/159445/

Bulk of the spread: Self Propagation
Inserts IFrame/ Script injections in all web pages in the victim’s machine
If victim = website admin, all his websites will be updated with infected pages.
Or steals FTP passwords from victims’ computer and updates the pages directly on the web server.

Movies College Fashion Sports .abc.xyz

PC Based Security for Malwares
Source: http://www.cyveillance.com/web/docs/WP_CyberIntel_H1_2009.pdf

Movies College Fashion Sports .abc.xyz

Prevention …
“ Process”.
Use linux-based dedicated machines for website administration.
But even the best process cannot be 100% effective because…

Indirect Risks: The Legitimate can also becomes Dangerous A Site B B Iframe Injection All internal and external users of the “clean” site A are also at risk now.

Accept the risk… the Alternative: Fast Detection and Quick Remedy
Contain the spread of infection.
Protect reputation of the website.

Detection Part 1:
Detect ALL External Sites Linking from your websites

2 Methods
Internal Scans- Scanners that reside in the web server and scan all web pages for external links.
External Scans- Crawlers, not residing in the web server, that will scan all pages from the internet.

Internal Scans
Pros
Will be exhaustive and will scan pages behind authentication.
Cons
Will affect web server performance and can even crash the server.

External Scans
Pros
Can be run as often as possible.
Has virtually no affect on the web server.
Cons
Will depend on network conditions.
Breadth and the Depth of the scan may not be exhaustive.

The Scanner Must:
Detect and list all external sites in a website.
Ideally NOT visit any external websites
Because it may put the system at risk.

Detection Part 2:
Detecting malware spreading sites in the list of external sites.

Behavior Analysis Detection Model
Visit the external site
Download suspected malware
Analyze it
And determine if it is malware or not.

fashion. abc.xyz efg.xyz
Iframe redirection
Malware
Legitimate
Dynamic Scan

Behavior Analysis
Expensive- requires a dedicated setup.
Slow- takes time to analyze all codes downloaded from external websites.
Newer malwares are designed to fool it- delayed activation etc.
Will not detect infected ‘site B’

Signature Based Detection Model
Downloads signatures of malware infected sites.
Compares the list of external sites to the signatures.

Multi Sourced Signatures
List of external sites.
Positive Matches

Signature Based
Cheap- can be done on any machine.
Several “freely” available sources of signatures.
Fast- comparison takes a fraction of the time.
Safe- malware is not downloaded on the machine.
Will detect infected ‘site B’.

Final Model
External Scanner/ crawler that will continuously scan the entire domain for external sites.
At least 2 sources of signatures. Update as frequently as possible.

Ideally…
Crawl time > Signature update time.
On every signature update, the list of external site from (n-1)th crawl should be used for full comparison.

On A Positive Match
Immediately remove the malware site link from the infected page.
Run AV and malware detection scans on the affected server.
Or quarantine suspected computers…
Change FTP password.

Multi Sourced Signatures
List of external sites.
Positive Matches
Continuous Crawl
Compare

Thank you
[email_address]

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nullcon 2010 - Signature based Malware Detection PoC for Websites

by n|u - The Open Security Community on Apr 02, 2010

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nullcon 2010 - Signature based Malware Detection PoC for Websites — Presentation Transcript