![]() ![]() Hacking techniques use DNS to exfiltrate data or tunnel command channels. Outbound connections, even DNS queries, are strong indicators of suspicious activity. Web servers by design always expect incoming connections. This doesn’t completely negate the utility of a firewall it just puts into perspective where the firewall would be most and least effective.Ī rule sure to reduce certain threats is to block outbound connections initiated by servers. The majority of attacks described in this book work over HTTP, effectively bypassing the restrictions enforced by a firewall. Sites typically only require two ports for default HTTP and HTTPS connections, 80 and 443. Mike Shema, in Hacking Web Apps, 2012 Restricting Network ConnectionsĬomplex firewall rules are unnecessary for web sites. These attacks range from abusing cross-site scripting, which results in universal cross-site scripting, to performing denial-of-service attacks against poorly constructed regular expressions. ![]() Putting together many of the ideas and techniques, users can see how a variety of filters can be bypassed and attacked. Both WAFs and client-side filters have filtering limitations which an attacker can exploit. Different types of filtering devices can be used to protect Web applications. After some practice, security penetration testers can learn to recognize the general strengths and weaknesses of WAFs, which can help them to hone their Web application attack skills. ![]() Spending some time with the administrative interfaces and/or bypassing the built-in filters is a great way to practice many of the techniques. Most open source WAFs have a publicly accessible demo application showing the effectiveness of their filtering, and sometimes the WAF's administrative interface as well. WAFs can be difficult to customize for a particular application, making it difficult to run them in “whitelisting mode.” It is common to find WAFs deployed in “blacklisting mode,” making them more vulnerable to bypasses and targeted attacks. Many commercial WAFs are available, along with several freely available (usually open source) alternatives. Web application firewalls (WAFs) are commonly used to detect (and sometimes block) Web attacks. David Lindsay, in Web Application Obfuscation, 2011 Publisher Summary Web application firewalls and client-side filters ![]()
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