install the selections, use: apt-get -u dselect-upgrade. Hardening sshDifficulty: Easy Application: ssh Although SSH is a pretty secure way to connect to your server,there are two simple changes you can make that will boost itssecurity even further. First, you almost certainly don't want peoplelogging in directly as root - instead, they should logon as a normaluser, then use the su command to switch over. You can change thissimply in the /etc/ssh/ssh_config file by adding the line: PermitRootLogin noNow the only way to get root privilges is through su, which meanscrackers now need to break two passwords to get full access. Whileyou are editing that file, find the line which says: Protocol 2, 1And change it to: Protocol 2This removes the option to fallback on the original SSH protocol, nowconsidered very vulnerable. Stopreplying to pingsDifficulty: Easy Application: sysctl While ping is a very useful command for discovering networktopology, the disadvantage is that it does just that, and makes iteasier for hackers on the network to target live servers. But you cantell Linux to ignore all pings - the server simply won't respond.There are a number of ways to achieve this, but the best is to usesysctl. To turn off ping replies: sysctl -w net.ipv4.icmp_echo_ignore_all=1To turn it back on, again use: sysctl -w net.ipv4.icmp_echo_ignore_all=0If turning off ping is too severe for you, take a look at the nexthack. Slow down pingratesDifficulty: Easy Application: sysctl You may want to keep the ability to reply to pings, but protectyourself from a form of attack known as a 'ping flood'. So how canyou manage such a feat? The easiest way is to slow down the rate atwhich the server replies to pings. They are still valid, but won'toverload the server: sysctl -w net.ipv4.icmp_echoreply_rate=10This slows the rate at which replies are sent to a single address. Clean up KDEon logoutDifficulty: Easy Application: bash On Windows there are plenty of programs that do stuff like cleanout your web cache, remove temporary files and all sorts of otherstuff when you logout. Wouldn't it be cool to do this on Linux too?With KDE, you don't need to even install any new software, as thestartkde script will automatically run scripts you put in specialplaces. First, you need to create a directory called shutdown in your .kdedirectory: mkdir /home/username/.kde/shutdownNow create a script to do any stuff you like on shutdown. Here is anexample: #!/bin/bash#clear up temp folderrm -rf ~/tmp/*#clear out cachesrm -rf ~/.ee/minis/*rm -rf ~/.kde/share/cache/http/*# delete konqueror form completionsrm ~/.kde/share/apps/khtml/formcompletionsNow make sure you set the correct permissions: chmod ug+x ~/.kde/shutdown/cleanup.sh(or whatever you called it). As well as cleaning up sensitive files,you can also have global shutdown scripts for all users, by placingthe script in your default KDE folder, in a subfolder calledshutdown. To find out which is your default KDE directory, try: kde-config --path exePassword-less sshDifficulty: Intermediate Application: ssh Tired of typing your password every time you log into the server?ssh also supports keys, so you'll only have to type in your passwordwhen you log in to the desktop. Generate a keypair on your desktopmachine: ssh-keygen -t dsa -C your.email@ddressEnter a passphrase for