Where can I find security updates?

As a root server customer, you are responsible for the administration of your
Linux server. Above all, the administration includes the constant updating of the
Linux system so that security holes cannot be utilized by attackers. This article
is intended to help you keep your server completely up-to-date, and to find out
about security holes and patches as quickly as possible.

Security glossary:
What is an exploit?
A program has an "exploit" when a user is able to use it "inappropriately" (i.e.
by attack) to gain user rights to which he is not entitled (e.g. root). The most
dangerous exploits are "remote roots", because these enable the attacker to
acquire root permissions via the network.

What is a patch?
Whenever software is updated, it is not necessary to reinstall the entire package.
Instead, you can just "patch" your current version simply by changing those parts
of the program that differ from the new version. Basically, either the source code
or the binary (executable program) of the software can be updated with a "patch".

What is a security hole?
A security hole doesn't have to be an exploit. It may be that the program in
question is working perfectly. One example is a DOS (Denial of Service) attack,
where the victim system is loaded to such an extent that the server services are
no longer able to react in the available time. The system may even crash.
Firewalls exist for this type of security hole. They will prevent an attacker from
using network packages to overload the system.

How do I find out about security updates?
Whenever new exploits are found, they are published on various news sites on the
Internet. It is usually sufficient to visit your Linux distributor's mailing list
and security news page every day to find out about any exploits.

How to plug a security hole?
If you have heard of a security hole and find that it has affected your system,
you will, of course, have to plug it on your server. Here too, the distributor of
your Linux system will be pleased to help you with an update, patch or bugfix for
the package in question. All you then have to do is feed it into your system -
and the gap is plugged (see also How do I install my own programs?)

How to set up a firewall?
There are several websites with good information on how to set up a firewall.
Here are several links to sites where you will find these instructions,
and other relevant subjects.

Linux 2.4 Packet Filtering HOWTO
Linux Networking-concepts HOWTO
Linux Firewall and Security How to Site (English)
Attack incidents (English)

SD2B2C702

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