Content related to computer security., i.e. content about policies, mechanisms, etc. needed make sure data is not leaked or corrupted and services available in all circumstances.

learn more… | top users | synonyms

11
votes
4answers
984 views

How exactly do people “crack” Unix/Linux Systems?

No im not looking to become a cracker or something like that, but Im trying to figure out the process (more from a programming perspective). So im assuming (guessing) a cracker's main goal is to gain ...
4
votes
5answers
158 views

Hiding work in account with multiple users

I'm currently working on an assignment in a cluster programming class. The class has been given an account on the cluster, so we can ssh in and do our work. The problem is that the one account is ...
7
votes
1answer
668 views

Opening port 80 but remain secure

I have a standard installation of Ubuntu 10.04, and have installed the LAMP stack so I can do some web development locally. On my router I have opened port 80 so I can develop with external services ...
5
votes
1answer
2k views

Disable random memory address generation in my programs

I'm reading "The art of exploitation" and would like to try some experiments, including reading from and writing to various memory address. I've created some simple programs and trying to overwrite ...
8
votes
1answer
362 views

Encrypted Booting

I want to boot the Linux from the /boot partition, and also want to encrypt this /boot partition. [ AFAIK, Grub is unable to find the kernel and initrd from an truecrypted partition or cryptsetup ...
2
votes
1answer
248 views

How do I make a certain command sudo-only on Debian?

What user and group should I chown it to? All admins are in 'admins' group. How do I chmod it?
2
votes
2answers
3k views

How to change dm_crypt aes/256 LVM password after install?

I installed Fedora 14 & Ubuntu 10.04 LTS on my PC. I used dm_crypt/LVM with aes256 in both installs (2 VolumeGroups, each encrypted, so there is 2 separated & encrypted linux distro on this ...
3
votes
1answer
179 views

Linux App that monitors log and add rules to iptables

I used to use a linux software that monitors logs like http, ssh, etc and if it detects that someone is trying to use brute force, it blocks that ip by adding a rule to iptables. I forgot what that ...
2
votes
2answers
593 views

Cannot understand chkrootkit's result

I couldn't understand the output of chkrootkit command: $ chkrootkit -q -r / /usr/lib/.libssl.so.10.hmac /usr/lib/.libfipscheck.so.1.hmac /usr/lib/firefox-3.6/.autoreg ...
5
votes
2answers
2k views

BCRYPT - Why doesn't the Linux Distributions use it by default?

Does OpenBSD use bcrypt by default? Why doesn't every modern Linux Distribution use BCRYPT? http://codahale.com/how-to-safely-store-a-password/ https://secure.wikimedia.org/wikipedia/en/wiki/Bcrypt ...
5
votes
4answers
391 views

SSH to untrusted machine

If I SSH to a remote server, is it be possible for the admins of that machine to use my SSH session to send data back down the connection and do something to my local PC? I use DSA keys and do not ...
5
votes
1answer
6k views

What is hvc0? (appearing in “who” list)

I have an Ubuntu Server, and when I type who, to see who's connected, I can see that there's a user connected, and instead of being logged to a pts/x, he's connected to hvc0. Is there something to ...
4
votes
1answer
878 views

Linux - why is kernel.shmall so low by default?

I run DB2 on Linux where I have to allocate the vast majority of memory on the machine to shared memory segments. This page is typical of the info that I've found about shmall/shmmax: ...
56
votes
7answers
51k views

What's the difference between /sbin/nologin and /bin/false

Technically, unless pam is set up to check your shell with pam_shells neither of these can actually prevent your login, if you're not on the shell. On my system they are even different sizes, so I ...
4
votes
2answers
5k views

Can I create a local only guest account?

Is it possible to create a "guest" account in Linux? by "guest" account I mean an account that does not require a password to log in graphically. I want this account for when people come over and are ...
6
votes
1answer
2k views

Lock screen w/ slock after a certain time?

I am running OpenBox in Arch Linux, how can I set it up so that I can have slock lock my screen after a certain amount of time (with no activity)? Thanks!
2
votes
2answers
1k views

GPG check regarding packages on various distributions

It's ok that the various linux distributions use gpg to verify e.g. new packages downloaded with http. But what happens if the server that holds the packages gets hacked? OK, they need a new gpg key, ...
0
votes
0answers
146 views

git and remote security with Encfs [duplicate]

Possible Duplicate: How do i encrypt git on my server? I wanted to create a user on my server to use as a private repository. I'd like the files to be encrypted. Encfs will timeout after ...
3
votes
1answer
119 views

Is it safe to leave a enc folder mounted?

I was looking at this and ecryptfs seems cool. I'd like to use it on my server to encrypt git pushes. I dont want to ssh in everytime to mount/unmount the encrypted folder. However once in a while ...
3
votes
1answer
2k views

Privoxy redirect rule for Wikipedia

I have a few Privoxy rules, that can redirect HTTP Wikipedia [en,de] traffic to HTTPS: (a little part from the "user.action" file) { ...
7
votes
2answers
242 views

Hibernate and security considerations

How do Linux and OSX handle sensitive memory pages (e.g. cryptographic keys) when running OS is suspended to disk? If the memory image written is encrypted, how are its keys handled?
0
votes
2answers
707 views

Is there a Debian security APT repository that allows access via ftp?

If I want security updates for Debian, I add the following line to /etc/apt/sources.list: deb http://security.debian.org <codename>/updates main Is there a repository that allows the http to ...
3
votes
3answers
285 views

Turning an old computer into a network firewall

I have an old Dell Dimension with two ethernet cards, and I need to turn it into a firewall. I've tried FireStarter and IPCop, but I don't think I'm setting them up right. Here's the setup that I'm ...
5
votes
2answers
808 views

make a 2nd root?

I was thinking, maybe i'd like to disable passwords for the root user and only use keys to log in. and if i need to login without keys have a 2nd user that is like root in everyway except has a ...
2
votes
2answers
324 views

What is the “Online Certificate Status Protocol”?

I use privoxy. In the user.action file i have a redirect rule and a few websites: { +redirect{s@http://@https://@} } .twitter.com .facebook.com Ok! it's working great, e.g.: if i visit any ...
9
votes
1answer
487 views

Is locking the screen safe?

See USB driver bug exposed as "Linux plug&pwn", or this link Two choices [GNOME, Fedora 14]: Use the gnome-screensaver Use the "switch user" function [gnome menu -> log out -> switch user] ...
3
votes
2answers
1k views

What directories/file permissions should i ensure are set?

I have a similar question about default software configuration. For this question i would like to ask What directories/file permissions should i ensure are set? Aprrently Is it normal to get ...
2
votes
3answers
1k views

Is there any chance that some of these processes are malicious?

My significant other and I are sometimes paranoid that a foreign government usually associated with last year's Gmail security breach may be attempting to gain access to our computers. There were a ...
2
votes
1answer
2k views

Ideas for securing OpenVPN on an OpenWrt router

I put an OpenVPN server on port 1194 on an OpenWrt 10.03 router: echo "nameserver 8.8.8.8" > /etc/resolv.conf; opkg update; opkg install luci-app-openvpn openvpn openssl-util openssh-sftp-server ...
2
votes
1answer
3k views

How to connect to OpenVPN with NetworkManager

I have installed an OpenVPN server on my OpenWrt 10.03 router [freshly flashed]: https://pastebin.com/raw.php?i=hRECWuf1 echo "nameserver 8.8.8.8" > /etc/resolv.conf; opkg update; opkg install ...
1
vote
1answer
130 views

Default configuration I need to change?

A few days ago I installed a new linux os. Today i realize /root has o+r (755) so EVERYONE is able to see my root sql password in /root/.my.cnf. I freaked out and simply changed /root to 750. My ...
7
votes
1answer
951 views

Why root's default shell is configured differently with other normal user account's default shell?

As I know, root's default shell is configured csh and normal user's default shell is sh in FreeBSD. And in Ubuntu, root is dash, normal user is bash. (refer: What's the Ubuntu's default shell?) Why ...
1
vote
1answer
1k views

IPTABLES rule for separating users

I have an OpenWrt 10.03 router [ IP: 192.168.1.1 ], and it has a DHCP server pool: 192.168.1.0/24 - clients are using it through wireless/wired connection. Ok! Here's the catch: I need to separate ...
2
votes
1answer
245 views

tripwire report - inode number

Hi I am investigating tripwire and have stumbled upon something which i am unsure about. in a tripwire report generated after i modified hosts.deny to include an extra # I noticed the inode number ...
18
votes
3answers
2k views

Is it secure to leave a root shell running in detached screen session?

I'm curious about the security of leaving a root shell running inside a detached screen session. I typically never do this. Aside from the potential of my non-root user account being compromised ...
6
votes
4answers
6k views

Debian: Which firewall for a newbie?

I have to install a firewall on my server (so without X Server). It's a debian lenny. If it is possible, I want to avoid the use of iptables. Is there a way to install/configure a firewall for a ...
3
votes
1answer
211 views

Is there a standard way to configure what policy iptables loads on startup under Debian?

I've just started playing with Debian 6.0 (Squeeze) in a VPS environment, as a way to learn more about system administration. One thing I'd like to configure is a default packet filtering policy. ...
6
votes
2answers
4k views

Write to a file without redirection?

I am writing a regular compiled application that needs to create a special file and write a magic cookie into it. I can’t write the file directly from the application, the system security model ...
4
votes
1answer
133 views

How can I run keychain in a way that only has the first shell prompt for keys on startup?

I open multiple shell tabs when I start KDE, and I've just added keychain to my ~/.shellrc the problem is that all the tabs prompt for key passwords when I login. This is quite annoying to do this. Is ...
1
vote
2answers
132 views

How would you create a user with the HOME_DIR field in /etc/passwd completely blank?

Closest I can come is: useradd --home / -r --shell /sbin/nologin someuser But this creates an entry into /etc/htpasswd that looks something like this: someuser:x:100:100::/:/sbin/nologin I want ...
6
votes
2answers
916 views

I/O-overhead of dm-encrypted device?

What would be the Read-/Write-overhead when using dm-crypt (LUKS) as full disk-encryption (including root partition) on a Linux-Desktop (Ubuntu)? I plan to stack it like so: LUKS > LVM > ext4 The CPU ...
1
vote
5answers
409 views

Does verifying packages enhance security and/or stability of a system?

RedHat/CentOS and Ubuntu both provide packages to verify the contents of a package. CentOS uses rpm -V. Ubuntu uses debsums. I've spoken to admins who run these tools to verify the packages on their ...
9
votes
2answers
1k views

What encryption does vim -x use?

I read man vim, :h -x and :h encryption none of this actually says what algorithm it's encrypted with.
2
votes
1answer
890 views

How to restore GnuPG key after reinstall?

I know that GnuPG is all about security, thus it's not giving many chance of retrieve private keys (otherwise anyone could do it) but I've got a private key, and my own rev.asc file. I had to ...
4
votes
1answer
237 views

What's the best way to configure shared filesystem directories? (beyond standard unix perms)

I have multiple users on my system. I'd like to have shared directories like music, video. pictures etc. The problems is that I want users to be able to write any new files to any directory, but not ...
5
votes
4answers
347 views

Is it possible to use pendrive as key for Linux system

I want to give high security for my linux box. So i planed to use my pen drive as key for my linux box. How can i do it ?
4
votes
3answers
273 views

Randomise or shred memory of an application

Is it possible to randomise or shred memory of a particular application just after its life ends, or better, whenever it deallocates some memory? A command-line utility like this would be perfect: ...
6
votes
2answers
276 views

Lock some accounts during some time periods

Is it possible to lock some accounts in order to be accessible only during specific time periods? For instance the account joe should only be accessible during office hours.
2
votes
1answer
518 views

How to update gnome keyring password?

Last weak I updated my password on my laptop. Then every time when I logged in, it would prompt for my old password to open the keyring for network manager. To fix this in a terminal I use rm ...
3
votes
1answer
339 views

Learning about iptables: Is this Slicehost example any good?

In preparation to eventually launch my first website, I've been playing with Ubuntu Lucid Server in a VM on my WinXP machine. I've been alternating between the Linode and Slicehost tutorials/articles ...