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Table Of Contents  CertiGuide to Security+
 9  Chapter 2:  Communication Security (Domain 2.0; 20%)
      9  2.3  The Web
           9  2.3.4.2  ActiveX

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2.3.4.3  Buffer Overflows
(Page 2 of 3)

How Are They Exploited?



A buffer overflow can be exploited directly by a malicious user in a variety of ways. For example, providing a bogus URL that is thousands of characters long to a web server has been known to crash a web server. The URL doesn’t have to be valid. It doesn’t have to point to a real web page location … the trick is just in jamming thousands of unexpected characters of any sort down the throat of the web server. At the end of the thousands of unexpected characters might be a bunch of binary data, which is designed to end up in just the right place in memory, that after the buffer overflow takes place, the computer will see that binary data as instructions, and run them.

Buffer Overflow

A buffer overflow occurs when a software program tries to copy too much data into too small an area of computer memory, causing the data to fill up that area and overwrite other areas of memory near it. This may crash the computer or enable an attacker to execute program code of their choosing on it.

Buffer overflow vulnerability can be exploited by providing a very large amount of data in response to a web form. In some situations, the data may include binary data designed to cause the server to execute particular functions when it receives the huge piece of data.



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