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Modern Operating Systems by Herbert Bos and Andrew...
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Modern Operating Systems by Herbert...
Modern_Operating_Systems_by_Herbert_Bos_and_Andrew_S._Tanenbaum_4th_Ed.pdf-M ODERN O PERATING S YSTEMS
Page 1005
CHAP. 11
the address space.
Recent work shows how running programs can be rerandom-
ized every few seconds, making attacks even more difficult (Giuffrida et al., 2012).
Heap hardening is a series of mitigations added to the Windows imple-
mentation of the heap that make it more difficult to exploit vulnerabilities such as
writing beyond the boundaries of a heap allocation, or some cases of continuing to
use a heap block after freeing it.
VTGuard adds additional checks in particularly
sensitive code that prevent exploitation of use-after-free vulnerabilities related to
virtual-function tables in C++.
Code integrity
is kernel-level protection against loading arbitrary executable
code into processes.
It checks that programs and libraries were cryptographically
signed by a trustworthy publisher.
These checks work with the memory manager
to verify the code on a page-by-page basis whenever individual pages are retrieved
from disk.
is a kernel-level mitigation that attempts to detect rootkits
designed to hide a successful exploitation from detection.
Windows Update
is an automated service providing fixes to security vulnera-
bilities by patching the affected programs and libraries within Windows. Many of
the vulnerabilities fixed were reported by security researchers, and their contribu-
tions are acknowledged in the notes attached to each fix. Ironically the security
updates themselves pose a significant risk.
Almost all vulnerabilities used by at-
tackers are exploited only after a fix has been published by Microsoft.
This is be-
cause reverse engineering the fixes themselves is the primary way most hackers
discover vulnerabilities in systems.
Systems that did not have all known updates
immediately applied are thus susceptible to attack.
The security research commun-
ity is usually insistent that companies patch all vulnerabilities found within a rea-
sonable time.
The current monthly patch frequency used by Microsoft is a com-
promise between keeping the community happy and how often users must deal
with patching to keep their systems safe.
The exception to this are the so-called
zero day
vulnerabilities. These are
exploitable bugs that are not known to exist until after their use is detected.
nately, zero day vulnerabilities are considered to be rare, and reliably exploitable
zero days are even rarer due to the effectiveness of the mitigation measures de-
scribed above.
There is a black market in such vulnerabilities.
The mitigations in
the most recent versions of Windows are believed to be causing the market price
for a useful zero day to rise very steeply.
Finally, antivirus software has become such a critical tool for combating mal-
ware that Windows includes a basic version within Windows, called
Antivirus software hooks into kernel operations to detect malware in-
side files, as well as recognize the behavioral patterns that are used by specific
instances (or general categories) of malware. These behaviors include the techni-
ques used to survive reboots, modify the registry to alter system behavior, and
launching particular processes and services needed to implement an attack.
Though Windows Defender provides reasonably good protection against common
malware, many users prefer to purchase third-party antivirus software.

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