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White Paper Access Protection in McAfee VirusScan Enterprise and
Host Intrusion Prevention
Access Protection in VirusScan Enterprise
A key component of VSE, Access Protection gives you flexibility to limit potential outbreak damage, even
before a .DAT file is issued. You can also close ports, monitor applications and email engines, block files
and directories, and trace and block infection sources.
Access Protection prevents unwanted changes to your computer by restricting access to specified ports,
files and folders, shares, and registry keys and values. It prevents users from stopping McAfee processes
and services, which are critical before and during outbreaks.
Access Protection for VSE uses predefined and user-defined rules to strengthen systems against virus
attacks. For instance, rules are used to specify which items can and cannot be accessed. Each rule can be
configured to block and/or report access violations when they occur, and rules can also be disabled.
The goal of this white paper is to provide an in-depth look at Access Protection and the importance and
detail of the rules, which are organized into categories based on their function. The paper will explain
the advantages and risks for Access Protection features, enabling you to determine which settings are
optimal for your environment.
Extending Access Protection with McAfee Host Intrusion Prevention
The November 2008 content release for McAfee Host Intrusion Prevention (Host IPS) included new
signatures that effectively duplicate the functionality of VSE’s Access Protection rules. For greater control
and flexibility, many customers have asked for the ability to manage these protections within Host IPS.
The new signatures are disabled by default and set to log only in Host IPS to prevent accidental changes
in your security posture and preferences. This white paper describes which Host IPS signatures map to
VSE rules where applicable.
McAfee
®
VirusScan
®
Enterprise (VSE) 8.7i, the leading enterprise-class anti-virus
software solution, uses true on-access scanning to identify, proactively block, and
safely eliminate viruses and potentially unwanted programs (PUPs) for optimal
business availability. Centrally managed with McAfee ePolicy Orchestrator
®
(ePO™)
and scalable for businesses of any size, VSE enhances the security of your company’s
computing systems by protecting them from programs that may be watching,
recording, and externally transmitting sensitive company information.
Securing networks against a wide range of threats—viruses, spyware, worms, rootkits,
and Trojans—is more challenging than ever. Whether you are a global enterprise or
a small or medium-sized business that has a full-time security staff, VSE ensures that
your endpoint servers, desktops, and laptops remain malware free. VSE proactively
stops and removes threats, extends coverage for new security risks, and reduces the
cost of managing outbreak responses. It even stops zero-day threats and mitigates
your window of vulnerability without an update.
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White Paper Access Protection in McAfee VirusScan Enterprise and
Host Intrusion Prevention
Access Protection Rules in VirusScan Enterprise
In the past, virus-scanning software depended primarily on the release of updated virus definition
(.DAT) files that instructed the software how to detect and defend against new virus attacks. The use
of .DAT files is still inherent in VSE; however, administrators now also have the ability to create rules that
strengthen systems against further infection and provide a layer of intrusion prevention.
In VSE, all predefined rule definitions are stored in the file vscan.bof. This file is digitally signed and is
updatable by the AutoUpdate process. The new rule-definition language used in vscan.bof allows a
single rule to protect multiple objects of different types (file, registry, port, and process). The new rule
language also allows inclusion and exclusion lists for the objects being protected. For example, a rule
can block access to c:\*.exe and c:\temp/*.exe except for **/notepad.exe.
Purpose and application of rules
Rules should be created with one or more of the following purposes in mind:
To prevent malicious code from running
•
To identify which computers have malicious code running
•
To prevent malicious code from spreading to other computers
•
To prevent a payload from damaging the local computer
•
Rules can be created to target a specific, newly discovered threat, or they can be predefined to provide
generic protection against future threats. For example, a rule might be used during the brief time
between a virus outbreak and the release of a new .DAT file by McAfee Avert
®
Labs. During this time, it
is important to stop the exploit from affecting the targeted systems and prevent it from spreading. In
many cases, VSE can facilitate a new .DAT update and apply operating system patches without allowing
the infection to spread. The rules are therefore not being used in place of virus definition files—they are
used to compliment them.
Processing Access Protection rules
Access Protection rules can be located in two different files, as well as the registry, and rules can be
processed in various ways based on the following conditions:
Vscan.bof
•
(located in the VirusScan directory) is the default Access Protection and buffer
overflow protection content file. This file is read first.
In an outbreak, Avert Labs may release an
•
extra.rul before a new vscan.bof is available. If an
extra.rul is present, (located in the VirusScan directory), it is appended.
User-defined rules are read from the registry and appended.
•
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White Paper Access Protection in McAfee VirusScan Enterprise and
Host Intrusion Prevention
Self Protection
Many malicious programs have attempted to disable VirusScan by stopping services and processes and
leaving the system vulnerable to attack. Self Protection is an important feature of VSE that prevents
malicious programs from disabling VirusScan, or any of its services or processes.
“Prevent McAfee services from being stopped”
Self Protection begins with the check box in the lower left corner on the main Properties screen, and
includes the following additional rules (listed throughout this document):
Prevent modification of McAfee files and settings
•
Prevent modification of McAfee Common Management Agent files and settings
•
Prevent modification of McAfee Scan Engine files and settings
•
Prevent termination of McAfee processes
•
Intention: When the Prevent McAfee services from being stopped check box is selected under
Access Protection, VSE will prevent anyone except the SYSTEM account from terminating McAfee
services. This protects VirusScan from being disabled by malicious programs that seek to circumvent virus
protection programs by terminating their services.
Note: This feature is currently not supported on 64-bit operating systems.
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Host Intrusion Prevention
Anti-spyware Standard Protection
This group of rules only applies if you have the AntiSpyware Enterprise Module installed. The rules for
VSE begin in the section titled “Anti-virus Standard Protection.”
“Protect Internet Explorer favorites and settings”
Intention: This rule is designed to prevent modification of Microsoft Internet Explorer configurations
and files by any process not listed in the rule’s exclusion list. A common tactic of malware is to change
the browser’s start page, and install favorites. This rule protects against certain start page Trojans,
adware, and spyware that modify browser settings.
Risks: There really aren’t any drawbacks to enabling this rule, as it simply blocks processes from making
changes to favorites and settings in Microsoft Internet Explorer.
ID and Name in Host IPS:
3890, Access Protection—Protect Internet Explorer favorites and settings.
Anti-spyware Maximum Protection
“Prevent installation of new CLSIDs, APPIDs, and TYPELIBs”
Intention: This rule prevents the installation or registration of new COM servers. Some adware and
spyware programs can install themselves as a COM add-on in Microsoft Internet Explorer or Microsoft
Office applications.
Risks: If you have an application that needs to install a COM add-on that isn’t already listed in the
exclusion list, it will be blocked. The installation of some common applications, like Macromedia Flash,
registers COM add-ons and may be blocked by this rule.
ID and Name in Host IPS:
3891, Access Protection—Prevent installation of new CLSIDs, APPIDs, and TYPELIBs.
“Prevent all programs from running files from the Temp folder”
This rule will block any executable from running from the Temp directory; however, this rule is much
more restrictive in that it stops nearly all processes from launching in the Temp folder. This provides the
most protection, but also has a higher chance of blocking a legitimate application from being installed.
Intention: Most viruses need to be run once by a person before infecting a computer. This can be done
in many ways, such as opening an executable attachment in an email, downloading a program from the
Internet, etc. For example, <http://vil.nai.com/vil/content/v_101034.htm>.
An executable needs to exist on the disk before Windows can run it. A common way for applications to
achieve this is to save the file in the user’s or system’s Temp directory and then run it.
One purpose of this rule is to enforce advice that is frequently given to people: “don’t open attachments
from email.” The other purpose of this rule is to close security holes introduced by application bugs.
Older versions of Outlook and Internet Explorer are notorious for automatically executing code without
the user needing to do anything but preview an email or view a website.
Risks: All applications that are protected by these rules offer alternatives to running executables, such
as saving them somewhere else on the disk and running from there. So the downside of the rules is that
users may need to learn a few extra steps before doing things they can do more quickly now.
Note: Enabling this rule may prevent some applications from functioning outright.
ID and Name in Host IPS:
3905, Access Protection—Prevent all programs from running files from the Temp folder.
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Host Intrusion Prevention
“Prevent execution of scripts from the Temp folder”
Intention: This rule prevents the Windows scripting host from running VBScript and JavaScript scripts
from the Temp directory. This would protect against a large number of Trojans and questionable web
installation mechanisms that are used by many adware and spyware applications. This rule may also
block legitimate third-party applications from being installed.
Risks: Since the email client downloads the script and then launches a legitimate Windows program
(cscript or wscript) to process the script, this rule cannot distinguish between scripts that have been
saved from a malicious email and those that have a legitimate reason for existing in the Temp directory.
This rule may therefore prevent some legitimate scripts from running.
ID and Name in Host IPS:
3893, Access Protection—Prevent execution of scripts from the Temp folder.
Anti-virus Standard Protection
“Prevent Registry Editor and Task Manager from being disabled”
Intention: This rule protects some Windows registry entries to prevent the disabling of the registry
editor and Task Manager. In the event of an infection, an administrator needs to have the ability to make
changes to the registry, or open Task Manager to stop active processes.
Risk: Preventing the registry editor and Task Manager from running can make the manual removal of
malicious code more difficult.
ID and Name in Host IPS:
3883, Access Protection—Prevent Registry Editor and Task Manager from being disabled.
“Prevent user rights policies from being altered”
Intention: Many worms attempt to locate accounts on network systems that have administrative rights.
Enabling this rule prevents malicious code from modifying the rights of users. This rule protects registry
values containing important Windows security information. For example, some viruses remove important
privileges from the administrator account; this rule blocks those changes.
Included processes:
all
Excluded processes:
installers
ID and Name in Host IPS:
3884, Access Protection—Prevent user rights policies from being altered.
“Prevent remote creation/modification of executable and configuration files”
Enabling this rule will prevent other computers from making a connection and altering executables, files
in the Windows directories, etc.
Intention: This rule forms a very cut-down version of the “make shares read-only” rule. First, the
extension list is reduced to file types that viruses usually infect. Second, the blocked action is just “write,”
which prevents infection but also allows new files to be created. This protects against fast spreading
worms or viruses, which traverse a network through open or administrative shares.
Risk: While there are reasons to copy executables around using Windows shares there are fewer, if any,
reasons to modify executables on remote systems. This is usually indicative of attack behavior. These
four rules are much less likely to false alarm than the broad “make shares read-only” rule but are also
less secure.
ID and Name in Host IPS:
There is no corresponding signature in Host IPS.
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“Prevent remote creation of autorun files”
Intention: Autorun files are used to automatically launch program files, typically setup files from
CDs. Preventing other computers from making a connection and creating or altering autorun.inf files
can prevent spyware and adware from being executed. There are a lot of spyware and virus programs
distributed on CDs. Microsoft has disabled autorun in Windows XP Service Pack 2.
Included processes:
system:remote
Excluded processes:
none
ID and Name in Host IPS:
There is no corresponding signature in Host IPS.
“Prevent hijacking of .EXE and other executable extensions”
Intention: This rule protects the .EXE and other keys under HKEY_CLASSES_ROOT. Some viruses alter
these keys to ensure that the virus is run when any other executable runs. Enabling this rule will prevent
spyware and malware from modifying important operating system and executable files.
Included processes:
all
Excluded processes:
installers
ID and Name in Host IPS:
3887, Access Protection—Prevent hijacking of .EXE and other executable extensions.
“Prevent Windows Process spoofing”
Intention: Many viruses and Trojans run use the name of a Windows process. This rule prevents files
from being created or executed with the most commonly spoofed names. The authentic Windows file
is excluded.
Risks: None
Included processes:
all
Excluded processes:
none
ID and name in Host IPS:
3888, Access Protection—Prevent Windows Process spoofing.
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Host Intrusion Prevention
“Prevent mass mailing worms from sending mail”
Intention: Many viruses and worms find email addresses on the infected system and send themselves
to these addresses. They do this by connecting directly to the email servers whose names they have
harvested from the local system. This rule prevents any process from talking to a foreign email server
using SMTP. By blocking this communication, a machine may become infected with a new mass-mailing
virus, but that virus will be unable to spread further by email. It prevents outbound access to SMTP ports
25 and 587 on all programs except known email clients listed as an exclusion.
Risks: Our list of exclusions cannot be complete—there are many third-party applications that send
email. These will stop working until their process names are added to the list of exclusions. To add a
process to the list of exclusions, highlight the rule, click Edit, and add the process name to the list of
processes to exclude.
Included processes:
all
Excluded processes:
common browsers and email clients
ID, Name in Host IPS:
There is no corresponding signature in Host IPS.
“Prevent IRC communication”
Internet Relay Chat (IRC) is the preferred communication method used by botnet herders and remote-
access Trojans to control botnets (a set of scripts or an independent program that connects to IRC). IRC
allows an attacker to control infected machines that are sitting behind network address translation (NAT),
and the bot can be configured to connect back to the command and control server listening on any port.
Intention: Many backdoor Trojans connect to IRC servers and receive commands from their authors.
For example, http://vil.nai.com/vil/content/v_98963.htm. By blocking this communication, even if a
system becomes infected with a new Trojan, it will be unable to communicate with the person or entity
controlling it.
Risks: If IRC is used within a company, or if these ports are used for some other purpose, then the rule
will block them until the processes using the ports are added to the exclusion list.
Included processes:
all
Excluded processes:
none
Blocked inbound ports:
TCP/UDP 6666-6669
Blocked outbound ports: TCP/UDP 6666-6669
ID and name in Host IPS:
There is no corresponding signature in Host IPS.
“Prevent use of tftp.exe”
Trivial File Transfer Protocol (TFTP) provides basic file transfer with no user authentication. Many Trojans
use TFTP because it is a rudimentary method to download additional code. Enabling this rule will prevent
anything except Windows Update from using it to download other malicious code to the system.
Intention: Some viruses spread by exploiting buffer overflows in vulnerable applications. Code is
injected into the process and then run. This code downloads the rest of the virus from the computer that
just injected the download code. Often, the download code uses the Windows TFTP client (tftp.exe) to
perform the download. Therefore, even if a system becomes infected with part of a new virus, it cannot
become fully infected because it cannot download the rest of the code.
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Host Intrusion Prevention
Risk: The most reported case where Windows needs access to tftp.exe is when installing a Windows
service pack. When the service pack installer cannot upgrade tftp.exe, the install fails, it is generally
advised to enable this rule, but disable it during the period when patches and service packs are
being installed.
Included processes:
all
Excluded processes:
Windows Update
ID and name in Host IPS:
3889, Access Protection—Prevent use of tftp.exe.
Anti-virus Maximum Protection
Intention: Anti-virus Maximum Protection provides common rules that protect most critical settings
and files from being modified. This level provides more protection, but may prevent the installation of
legitimate software. If you cannot install software, we recommend that you disable Access Protection
Maximum Protection first, and then enable it again after installation.
Risk: Maximum Protection rules should be used with caution as they can block common activities
such as installation or execution of certain applications or processes. It is recommended that Maximum
Protection rules be initially enabled for report only in order to determine if exclusions will be required.
“Prevent svchost executing non-Windows executables”
Intention: Svchost.exe is a system process belonging to the Microsoft Windows operating system,
which handles processes executed from .DLLs. This program is important for the stable and secure
running of your computer and should not be terminated. Because this is a key component of Windows,
attackers attempt to use this process to register their own .DLLs that are not part of Windows. This rule
makes svchost.exe only load Windows service .DLLs.
Included processes:
svchost.exe
Excluded processes:
none
ID and name in Host IPS:
3894, Access Protection—Prevent svchost executing non-Windows executables.
“Protect phonebook files from password and email address stealers”
Intention: This rule prevents malicious code from reading the list of the user’s contacts, which are
stored in rasphone.pbk files in the user’s profile directories.
Included processes:
all
Excluded processes:
typical processes that access the address book
ID and name in Host IPS:
3895 (2), Access Protection—Protect phonebook files from password and email address stealers.
“Prevent alteration of all file extension registrations”
Intention: This is a stricter version of the “Anti-virus Standard Protection: Prevent hijacking of .EXE and
other executable extensions” rule. Instead of just protecting .EXE, .BAT, etc., it protects all the extension
options under HKEY_CLASSES_ROOT.
Documents you may be interested
Documents you may be interested
