This month, we finish our three-part series on hardening Linux systems. As we’ve seen, hardening is the process of reconfiguring an “out of the box” Linux distribution to make it more secure.
This month, we finish our three-part series on hardening Linux systems. As we’ve seen, hardening is the process of reconfiguring an “out of the box” Linux distribution to make it more secure.
In the first column in this series, we considered physical system security and installation choices. In the second column, we discussed how to configure the kernel, how to alter the boot process, and how to modify or disable system services to thwart intruders. This month, we change our focus from what software and services are provided on the computer to how users actually use it. We’ll see how to secure local file systems, how to restrict insecure root access, and how to configure user authentication. Finally, we’ll discuss some things you can do to keep your system safe from harm.
Securing Local File Systems
A well-hardened system not only thwarts outside intruders, it also protects against abuse perpetrated (intentionally or accidentally) by any user (whether authorized or unauthorized).
One subsystem that deserves special consideration is the file system. Hardening the file system safeguards the contents and attributes (protection bits, owner, etc.) of every file in the local file system. To secure the local file system, you have to conduct an audit and modify a variety of settings to provide only the minimum access required. (Additional, complementary information about file permissions can be found in this month’s Power Tools column on pg. 40.)
For example, look for inappropriate file and directory…
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