VULNERABILITIES IN WEB APPLICATIONS
By Raymond Ankobia

This is by no means an exhaustive list but an indication of some serious flaws exploited by hackers. Hacking Exposed: Web Applications (ISBN 007222438X) as a good source for the subject area.

Buffer Overflow Attack: Usually perpetrated in a form of stack, heap or format string attack [3]. Without doubt, one of the oldest problems exposed by poor programming; yet attacks continue to be perpetrated on large scale, simply due to lack of rigorous security routines in web applications. To get the system to run their own code, attackers construct an input string sometimes with other malicious code that is long enough to overrun memory space assigned to it [7]. By doing so, this spills over and overwrites the stack below, overwriting what was initially in that address space. If the code contains malicious payload, it may subvert the system and escalate any privileges it may have garnered.

SQL Injection Attack: Most e-commerce web sites use dynamic content to attract and appeal to potential customers by displaying their wares using dynamic SQL queries and front-end scripts. An attacker could inject special characters and commands into a SQL database and modify the intended query. Chaining additional commands with intent of causing unexpected behavior could alter the meaning to a query. Not only could the attacker be able to read the entire database, but also in some circumstances, alter prices of these commodities.

Cross Site Scripting Attack: (XSS Attacks) This attack is executed by embedding malicious message in an HTML form [4] [3] and posting it as a message to say a newsgroup or bulletin board. By viewing the message, the user unintentionally gets the code interpreted and executed by the web browser triggering its associated payload.

Input Validation Attack: Typically used by most active attackers to check for client side validation of fields and if successful then try to escalate privileges gained [3]. Poorly validated client-side (typically a web browser) allows an attacker to tamper with parameters sent to the server. Server-side may also compromised if trust is implicit and validation poorly executed from the client-side.

Phishing Attack: This attack is mainly executed due to vulnerability in some versions of web browsers. Attackers are able to create bogus websites and masquerade as legitimate commercial ones. They normally operate by sending spoofed emails to unsuspecting customers, advising them to visit their bank's website to reactivate or update their accounts. The embedded addresses in these emails tend to have some hidden characters cleverly constructed to make the page appear to be a legitimate one. On clicking the embedded website address, the unsuspecting user is redirected to a fake website where the credentials and details of bank accounts are taken and later used to empty the accounts.

[4] This anomaly is due to obfuscation techniques used by the URL to parse information. URL may be parsed in different ways using decimal, hexadecimal and dWord format. A particular vulnerability in Internet explorer allowed an attacker to construct and hide information by simply using the @ symbol in ways that makes it possible to redirect traffic to bogus sites.

Mobile code: Most common languages used for developing mobile code include Java, ActiveX control and Shockwave. Traditionally the programme gets downloaded from a web server onto the customer‚s machine. Environments used for execution include Virtual Machines (in browsers) or downloadable plug-ins. These programmes could be maliciously crafted to subvert the security and system functionality by causing crashes and disruption of normal operating environment.

Insecure Configuration Management: The communicating parties end points, especially their web servers, are poorly configured. Often ignored, but the area most attacked by hackers as a way of bypassing security offered by encryption and other security mechanisms [4]. Apache and IIS dominate commercial deployment of web servers and some of the earlier releases are riddled with bugs. Simply installing these applications with default settings is a bad practice. Poorly programmed sample scripts are exploited by attackers who may easily take control of the server resources.

Google Hacking: Google's search engine traverses the Internet, crawling websites, and taking snapshots of each web page it examines and caches its results. Next time a query is received, the search is performed on these cached pages, allowing for faster retrieval [4]. Hackers exploit these caches for vulnerable sites. The mechanism used by Google is explained in great depth in a white paper written by Foundstone (www.foundstone.com) called SiteDigger,. Tools such as these are the Swiss army knives of hackers. Using search engines, hackers find vulnerability scanning reports and intrusion detection alerts and log files. These are then used to find suitable targets to exploit.

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