Hacker’s Diary 1

Secure Mount Point

WassUp guys !!…Well I am studying too many things about network security and Operating system so I decided to share

that with everyone .So the main aim of my hacker’s diary series is to tell people ways to remain more secure and surf internet freely without any fear of getting attacked .And everyone know what is networking …its all computer coming together and sharing things…with some sharing…and some stealing..  this is one of my own definition but still I don’t have any copy write on that .

so lets start with hard drive. We all known most of our data is stored in our hard drives and it is the primary way of interacting with a unix (or window) machine.So it is desirable to limit what a intruder (I) can access () if he gains access on your computer.

So one easy way of doing that is  the use of restrictive mount point.

A mount option is a flag that controls how the filesystem may be accessed. It is passed to the operating system kernel's code when the filesystem is brought online. Mount options can be used to prevent files from being interpreted as device nodes, to disallow binaries from being executed, and to disallow the SUID bit from taking affect (by using the nodev, noexec, and nosuid flags). Filesystems can also be mounted read-only with the ro option.

These options are specified from the command line by running mount with the -o flag. For example, if you have a separate partition for /tmp that is on the third partition of your first IDE hard disk, you can mount with the nodev, noexec, and nosuid flags, which are enabled by running the following command:

# mount -o nodev,noexec,nosuid /dev/hda3 /tmp

An equivalent entry in your /etc/fstab would look something like this:

/dev/hda3 /tmp ext3 defaults,nodev,noexec,nosuid 1 2

There are a number of ways that an attacker can still circumvent these mount restrictions. For example, the noexec option on Linux can be bypassed by using /lib/ld-linux.so to execute binaries residing on such filesystems. At first glance, you'd think that this can be remedied by making ld-linux.so nonexecutable, but this would render all dynamically linked binaries unexecutable. So, unless all of the programs you rely on are statically linked (they're probably not), then the noexec option is of little use in Linux. In addition, an attacker who has already gained root privileges will not be significantly hampered by filesystems mounted with special options, since these can often be remounted with the -o remount option. But by using mount flags, you can easily limit the possible attacks available to a hostile user before he gains root privileges

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