Messages in this thread |  | | Subject | NT:n ongelmia... | From | (Jari Raitavuo) | Date | Sat, 21 Dec 1996 20:57:00 +0200 |
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--- Forwarded message --- Date: Fri, 20 Dec 1996 09:12:19 +0200 (GMT) From: Oskar Pearson <oskar@is.co.za> Subject: NT vulnerable to attack on CPU
> http://www.pcweek.com/news/1216/18ent.html > > December 18, 1996 5:45 PM ET > _NT vulnerable to attack on CPU_ > _By Eamonn Sullivan_ > > Errors in the way Windows NT schedules concurrently running > applications leave it vulnerable to a simple, but very effective, > denial of service attack, according to a Windows NT expert. > > "This is a wide-open hole just waiting for exploitation by an ActiveX > control," said Mark Russinovich, a consulting associate with Open > Systems Resources Inc. who discovered the vulnerability this week. The > flaw is particularly serious, since it can be easily exploited by an > ActiveX control or by a Netscape plug-in. > > Russinovich wrote a simple utility that, while running with no special > security privileges, is able to take complete control of any Windows > NT server or workstation, rendering it useless for any other > applications. The algorithm used by Windows NT to protect itself > against such CPU-hogging attacks appears to be seriously flawed and > ineffective, Russinovich said. > > The source code for the utility, which is called CpuHog, is available > on the Web at www.ntinternals.com. > > _How it works_ > > Basically, Russinovich's program exploits a vulnerability in the way > Windows NT schedules the execution of processes. > > Applications can set their own priority level, which affects how often > Windows NT allows those applications to run. An application running > under a user account with administrative privileges can set its > priority to any of 32 levels, with the highest level giving it more > time slices. Applications running under accounts without > administrative privileges can set their priority to any of the first > 16 of those levels. > > CpuHog sets its priority to the highest level available, which is > level 16 when run by a normal user. Windows NT attempts to deal with > CPU-hogging applications by boosting the priority of other > applications. However, Russinovich found that Windows NT will only > boost applications as high as level 15. Thus, all other applications - > even system utilities such as Task Manager - never get a chance to > execute while CpuHog is running. > > PC Week Labs was able to duplicate Russinovich's findings. When run on > Windows NT 4.0, for example, the only way to regain control once > CpuHog was executed was to reset the PC. > > _Old problem _ > > Hogging the CPU is one of the oldest known forms of denial of service > attack. So old, in fact, that many operating systems have developed a > defense. Many forms of Unix allow administrators to set limits on CPU > usage by user - limiting any one user to 50 percent of available CPU > cycles, for example. > > Almost all forms of Unix also automatically decrease the priority of > the highest-priority processes when applications become starved for > CPU time, which is the opposite of what Windows NT does. > > Russinovich said Microsoft could get around the problem fairly easily > in one of two ways: Either increase the maximum priority given to > other, CPU-starved applications above level 15, or increase the > priority of the Task Manager above level 16, so that it can be used to > end CPU-hogging applications. > > Microsoft officials contacted for this story did not have a comment, > other than to say they are researching the problem. > > ÄLINKÅ > > _Copyright(c) 1996 Ziff-Davis Publishing Company. All rights reserved. > Reproduction in whole or in part in any form or medium without express > written permission of Ziff-Davis Publishing Company is prohibited. PC > Week and the PC Week logo are trademarks of Ziff-Davis Publishing > Company. PC Week Online and the PC Week Online logo are trademarks of > Ziff-Davis Publishing Company._ > > > _Send mail to PC Week_ >
Oskar
--- Forwarded message ---
Että ei se ihan täydellinen ole NT vieläkään...
Jari
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