Tag Archives: exploit

Timing Attacks in Web Applications

When code is executed by a machine it takes some time to do so. Execution time ranges from nanoseconds to months and years and even more (think bruteforcing). Web applications construct output producing, in most cases, very short delays (think the time it takes to show Google search results after typing in the query). Depending on what output is request, how it is requested and what the input is web applications can vary their execution time.

Timing Attacks in Web Applications

In this article we’re going to exploit some of the open-source content management systems available using delays in its execution under differing conditions to evoke distinct differences in execution time, which allow us, as attackers, to make some useful conclusions.

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WordPress DoSnet

…or how to build your own WordPress-powered denial-of-service network

Pingbacks have been part of the WordPress since the very beginning. One of my previous articles, titled WordPress Pingback Attacks explores two types of denial-of-service attacks that leverage Pingback request processing in WordPress. If you do not know how Pingbacks work, I suggest taking a quick crash-course here.

WordPress Denial of Service DoSNet

One of the attacks is a Layer 7, direct denial-of-service attack, performed by a handful of machines targeted at a single WordPress XML-RPC server with pingbacks enabled. Its purpose is to deplete the server of memory resources by forcing it to download and parse a target URL, which is specifically crafted to heighten resource usage while parsing. Up to 6:1 peak-memory-usage-to-download-size ratios have been reliably reproduced. There’s a bug that allows 5 times as much usage (i.e. 30:1 inflation ratios) when setup properly (WordPress 3.4 will suffer from it as well).

The second attack is a Layer 4 (typically bandwidth-exhaustion), reflected distributed denial-of-service attack which utilizes publicly available WordPress sites on servers of any size and is the subject of this article. Buckle up, off we go.

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