247 lines
4.4 KiB
HTML
247 lines
4.4 KiB
HTML
<HTML
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><HEAD
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><TITLE
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>Disable ICMP Redirect Acceptance</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.60"><LINK
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REL="HOME"
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TITLE="Securing and Optimizing Linux"
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HREF="index.html"><LINK
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REL="UP"
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TITLE="General System Security"
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HREF="gen-syssecured.html"><LINK
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TITLE="Enable TCP SYN Cookie Protection"
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HREF="chap5sec56.html"><LINK
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REL="NEXT"
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TITLE="Enable always-defragging Protection"
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HREF="chap5sec58.html"></HEAD
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CLASS="section"
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BGCOLOR="#FFFFFF"
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><TR
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><TH
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COLSPAN="3"
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ALIGN="center"
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>Securing and Optimizing Linux: RedHat Edition -A Hands on Guide</TH
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></TR
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><TR
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><TD
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WIDTH="10%"
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ALIGN="left"
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><A
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HREF="chap5sec56.html"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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ALIGN="center"
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VALIGN="bottom"
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>Chapter 5. General System Security</TD
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><TD
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WIDTH="10%"
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ALIGN="right"
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VALIGN="bottom"
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><A
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>Next</A
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CLASS="section"
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><H1
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CLASS="section"
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><A
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NAME="AEN4131"
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>5.28. Disable ICMP Redirect Acceptance</A
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></H1
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><P
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> When hosts use a non-optimal or defunct route to a particular destination, an ICMP redirect packet is used by routers to inform the hosts what the correct route
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should be. If an attacker is able to forge <SPAN
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CLASS="acronym"
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>ICMP</SPAN
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> redirect packets, he or she can alter the routing tables on the host and possibly subvert the
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security of the host by causing traffic to flow via a path you didn't intend. It's strongly recommended to disable <SPAN
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CLASS="acronym"
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>ICMP</SPAN
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> Redirect Acceptance to
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protect your server from this hole.
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<DIV
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CLASS="mediaobject"
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><P
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><IMG
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SRC="images/Version6.1.gif"
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ALT="version 6.1 only"
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></IMG
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></P
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></DIV
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>
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="programlisting"
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> [root@deep] /# for f in /proc/sys/net/ipv4/conf/*/accept_redirects; do
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> echo 0 > $f
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> done
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</PRE
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></TD
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></TR
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></TABLE
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>
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="screen"
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> [root@deep] /#
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</PRE
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></TD
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></TR
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></TABLE
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>
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Add the above commands to the <TT
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CLASS="filename"
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>/etc/rc.d/rc.local</TT
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> script file and you'll not have to type it again the next time you reboot your system.
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</P
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><P
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> <DIV
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CLASS="mediaobject"
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><P
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><IMG
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SRC="images/Version6.2.gif"
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ALT="Version 6.2 only"
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></IMG
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></P
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></DIV
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>
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Edit the <TT
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CLASS="filename"
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>/etc/sysctl.conf</TT
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> file and add the following line:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="programlisting"
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> # Disable ICMP Redirect Acceptance
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net.ipv4.conf.all.accept_redirects = 0
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</PRE
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></TD
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></TR
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></TABLE
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>
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You must restart your network for the change to take effect. The command to restart manually the network is the following:
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<TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="screen"
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> [root@deep] /# /etc/rc.d/init.d/network restart
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Setting network parameters [ OK ]
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Bringing up interface lo [ OK ]
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Bringing up interface eth0 [ OK ]
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Bringing up interface eth1 [ OK ]
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</PRE
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></TD
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></TR
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></TABLE
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>
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Take Note that the above command for Red Hat Linux 6.1 or 6.2 will disable Redirect Acceptance Packets on all
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your interfaces lo, ethN, pppN etc.
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</P
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></DIV
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><DIV
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CLASS="NAVFOOTER"
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><HR
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ALIGN="LEFT"
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WIDTH="100%"><TABLE
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WIDTH="100%"
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BORDER="0"
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CELLPADDING="0"
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CELLSPACING="0"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="chap5sec56.html"
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>Prev</A
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></TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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>Home</A
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></TD
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WIDTH="33%"
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ALIGN="right"
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HREF="chap5sec58.html"
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>Next</A
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>Enable TCP SYN Cookie Protection</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="gen-syssecured.html"
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>Up</A
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></TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Enable always-defragging Protection</TD
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></TR
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></TABLE
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> |