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IMPORTANT
NOTE: This document is based on FreeBSD. The concepts should be similar across operating
systems, but the commands will very likely be different.
Also, never assume the directory structures exist in your system
as written in the document. Never blindly follow security
instructions -- read, review, compare, apply as it fits your
system.
The steps noted below will
increase the level of hardening of your operating system.
These steps will remove groups and
users not used by Internet servers, and set appropriate
permissions for system programs. Please note that when you
see a zero (0) in the last chmod permission bit, it means that
the world has no permission.
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Log into each server as root. Then
copy and paste the following to your command line to execute (please
double check directory locations as applicable):
3. Modify Kernel settings to increase
security:
sysctl -w kern.securelevel=2
sysctl -w net.inet.tcp.log_in_vain=1
sysctl -w net.inet.udp.log_in_vain=1
4. Edit /etc/defaults/rc.conf and /etc/rc.conf and make the
following changes:
icmp_drop_redirect="YES"
icmp_log_redirect="YES"
kern_securelevel_enable="YES"
kern_securelevel="2"
tcp_extensions="NO"
tcp_keepalive="YES"
icmp_bmcastecho="NO"
icmp_bandlim="YES"
5. Edit /etc/sysctl.conf and make the following
changes:
net.inet.tcp.log_in_vain=1
net.inet.udp.log_in_vain=1
kern.securelevel=2
net.inet.ip.check_interface=1
net.inet.tcp.recvspace=65535
net.inet.tcp.sendspace=65535
kern.fallback_elf_brand=3
net.inet.tcp.syncookies=0
net.inet.icmp.bmcastecho=0
net.inet.icmp.maskrepl=0
net.inet.icmp.icmplim=200
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IMPORTANT
NOTE: This document and all
linked document is being provided as a good will gesture to the
Parallels H-Sphere community and to others who may benefit from its use.
Dynamic Net, Inc. makes no representations implied or explicit
as to their value or warranty. Dynamic Net, Inc. will not be
held liable for any damage resulting in the application of the
steps and procedures noted. If you feel uncomfortable at
all about doing any of the steps, make a complete system backup
and hire a third party like
We Manage Servers
to do the work for you.
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