Black Hat Europe Buffer overflow bugs, for years the most prevalent type of security vulnerability, will become a thing of the past as crackers realise the potential of different ways to exploiting Windows machines.
Sloppy programming practices (the root cause of buffer overflow vulnerabilities) give rise to security bugs where arbitrary and malicious code can be injected into a system, through a carefully crafted malformed data entry.
Generally, this spurious input is much longer than a program expects, causing code to overflow the buffer and enter parts of a system where it may be subsequently executed. The technique has been successful used against both Unix and NT machines on numerous occasions.
Halvar Flake, "Reverse Engineer" at Black Hat Consulting, said such standard stack-smashing overflows are getting rarer in well-audited code, so crackers will turn to fresh ways of executing arbitrary code.
During a well received presentation at last week's Black Hat conference in Amsterdam, Flake showed how heap overflow attacks could be used to write more or less arbitrary data to more or less arbitrary locations. He described these as Third Generation Exploits on NT/Win2k Platforms, something explained in greater detail here, and although he told us it's a term he invented himself, we're happy to go along with it since we liked the cut of his jib.
Such third generation exploits mean it is possible to subvert the logic of a Windows app by modifying its variables.
He also outlined future cracker strategies involving creating a large number of threads in a multithreaded environment, which make an exploit "80-90 per cent reliable and independent of NT/Win2000/XP version, service pack and hot fix".
Heap overflow exploits (such as format string bugs and particularly malloc()/free()-manipulations) give attackers two powerful techniques.
Such tactics have been used, and documented, on *nix platforms and the value of Flake's work is to highlight the risk of the exploitation of the technique on NT/Win2k boxes. ®
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