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The 10 worst Web application-logic flaws that hackers love to abuse

By Ellen Messmer
May 3, 2012 06:33 AM ET

Network World - Hackers are always hunting to find business-logic flaws, especially on the Web, in order to exploit weaknesses in online ordering and other processes. NT OBJECTives, which validates Web application security, says these are the top 10 business-logic flaws they see all the time.

1. Authentication flags and privilege escalation

Since applications have their own access-control lists and privileges, if the implementation of the authorization is weak, it opens up vulnerabilities that can be exploited, such as accessing another's content or becoming a higher-level user with greater permissions. What's needed is identifying parameter names that have something to do with ACL/permission that could become a target, and the tester can use fuzzing tools to try and change bit patterns or permission flags, which may show the point at which exploitation, escalating privileges or bypassing authentication can be achieved by an attacker.

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2. Critical parameter manipulation and access to unauthorized information/content

HTTP GET and POST requests are typically accompanied with several parameters when submitted to the application, typically in the form of name/value pairs, JSON, XML and so forth, but they can be tampered with and guessed by predicting. Tests for this look for easily guessable values and whether a parameter's value can be changed in order to gain unauthorized access.

3. Developer's cookie tampering and business process/logic bypass

Cookies are often used to maintain state over HTTP, but developers are not just using session cookies, but are building data internally using session-only variables. Application developers set new cookies on the browser at important junctures which exposes logic holes. The danger is that these cookies can be reverse engineered or have values that can be guessed or deciphered and attackers try to identify these holes that are easy to exploit. Tests here typically involve analysis of cookies delivered during profiling, and looking for easily guessable values, and whether a cookie value can be changed.

4. LDAP parameter identification and critical infrastructure access

LDAP is becoming an important aspect for large applications and may get integrated with "single sign-on" as well. Many infrastructure layer tools like SiteMinder and Load Balancer use LDAP for both authentication and authorization. LDAP parameters can carry business-logic decision flags that can be abused or leveraged. Attackers can find business-layer bypasses and logical injections if the application is not doing enough validation. Tests for this focus on finding parameters linked with LDAP, such as those taking email or usernames, which are prospective targets.

5. Business constraint exploitation

The application's business logic should have defined rules and constraints, but if poorly designed, attackers can crawl them and browse through hidden fields and understand their context. So it's necessary to test hidden parameters and values, checking business-specific calls that can become a target and manipulated.

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Reprinted with permission from Story copyright 2012 Network World, Inc. All rights reserved.
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