Questions tagged [security]

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.

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2answers
191 views

Signing/Checksumming the kernel to prevent/detect manipulation

All my partitions are encrypted (/ and /home), but the /boot partition has to remain unencrypted and is open for manipulation. I was thinking about hashing the kernel on bootup and checking the result ...
0
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2answers
156 views

Where to handle packets between clients?

"Server": 192.168.1.1 I want to "theoretically" disable that the clients can "ping" each other. Can i use an iptables rule for it? e.g.: iptables -A FORWARD -m iprange --src-range 192.168.1.2-192....
3
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1answer
5k views

iptables rule to allow access to internet

I made default policy of my machine- iptables -A INPUT -j REJECT #DROP ALL PACKETS TO INPUT CHANNEL INPUT channel has been blocked. Now I want to allow only some specific services like I should be ...
3
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3answers
561 views

Setting execution right to whole directory - is it good or bad idea?

I have a zip file containing lot of files and directories for a certain application which should be running on Linux. Some files needs to be set as executable, but the zip file format afaik does not ...
1
vote
1answer
911 views

LoJack protection and recovery for Unix/GNU/Linux running systems?

The LoJack theft protection and recovery system looks very impressive, especially that they will find and return your computer for you, but the software is for Windows and OS X only. Is there an ...
6
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3answers
764 views

Unix users, groups, and permissions

I don't understand unix users, groups, permissions, etc. For example, things managed by the chmod, chgrp, usermod, groupadd, etc. commands. How do all these things work?
2
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2answers
1k views

How to deny rdesktop access to others?

Someone keeps trying to connect to my Ubuntu machine through remote desktop. Is there any way I can determine who it is, and permanently block access to my machine?
2
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1answer
2k views

How to find out that someone is using a Keylogger on the machine I am using?

HW/SW/whatever keyloggers are there. How to find out? E.x.: Regularly check the cable of the keyboard, because there could be HW keyloggers: http://i.imgur.com/TeMwo.jpg But what about other HW ...
6
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1answer
3k views

SSH Public key comment separator

I've created a SSH authentication key (with ssh-keygen) in two different servers, both with a useful comment, but the public key of one server has == between the key and the comment, while the other ...
1
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1answer
710 views

Best practices for secure, separated virtualhost LAMP environment

What are the best practices for a Debian Squeeze + Grsecurity/PAX based system when multiple, and therefore insecure, websites must run on the same server? I mean how can I mitigate an attack, so that ...
0
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1answer
3k views

How to really security a linux-mint-desktop?

I'm installing some security software in my mint9Gnome. I first went to Firestarter and looks like a pretty start. Now I'm going to OSSEC and want some good tools to search my logs too. Thinking ...
1
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1answer
1k views

rpc.statd and avahi-daemon listening on all networks?

Background: - I'm running a home Debian GNOME desktop connected to the internet through an ethernet cable to an ethernet router. - I have a printer connected directly to my PC with a USB cable. - My ...
5
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2answers
4k views

Directory/files owned by a non-existent user

A user has created a directory with files, but the user does not exist in /etc/passwd or /etc/group. The system is a Fedora server with an FTP server and proxy which redirects to a CentOS server with ...
4
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4answers
392 views

Internet SSH Server Security Considerations

What steps should I take to reasonably secure my linux desktop before opening sshd to the Internet so I can connect from anywhere?
11
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2answers
17k views

How do you protect a plain text credentials file with the username and password?

I am trying to setup an auto-mounting network drive. The network drive requires a user/pass. In the man page for "mount.cifs" there are two ways to provide the user/pass. [not recommended] put the ...
5
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1answer
352 views

Confused about PAM configuration stanza and the roles of the control-flag parameters

I just begun studying for the RHCE. While on the topic of PAM configuration, I was a little perplexed with this stanza from /etc/pam.d/system-auth: auth required pam_env.so auth ...
3
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4answers
1k views

sudo without password - security? [duplicate]

Possible Duplicate: What specific vulnerabilities am I creating by disabling the sudo password? I'm involved yet again in the old argument on whether sudo without password is secure enough or not....
3
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2answers
930 views

Security with Kernel IP Forwarding Enabled

I recently enabled IP Forwarding on a production web server that also acts as a VPN server. What, if any, security issues did I just set myself up for? And are there any iptables rules I should set ...
5
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1answer
3k views

I don't want other users see my processes in ps aux. I have root. It's Debian. How to use grsec?

I installed 'linux-patch-grsecurity2' and it has some sort of interface. ~$ sudo gradm2 gradm 2.1.14 grsecurity administration program Usage: gradm [option] ... Examples: gradm -P ...
4
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1answer
208 views

Running proprietary software on Linux safely [closed]

As a summer project, I'm looking to prevent any piece of proprietary software like many games I run from having access to my personal files. After looking a lot at sandboxing, I've decided that ...
3
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1answer
182 views

mounting volume protected against user access

I need to mount a directory in a way that prevents user accessing it. However I need to have access to all attributes (including permission) from root. Is following method safe or is there a way ...
10
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1answer
336 views

Does ssh-agent store my passphrase?

Is it possible to determine the passphrases of private keys added to ssh-agent? I'm thinking along the lines of someone with root privileges trying to find out my passphrase after I have added the ...
2
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1answer
608 views

Debian unstable chroot security issues

This page describes how you can use the debootstrap utility to install a base Debian unstable/sid system on an existing Linux machine. The new install is accessible using chroot. When doing this, ...
2
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1answer
2k views

root password changed automatically

I have my system on dual boot (win7 and RHEL 6). I have 2 user account on RHEL 6. A normal user and a root user. I put passwords of both accounts same. It was working fine from 5 6 days. Yesterday I ...
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1answer
220 views

What are the cons of posting dmidecode output publicly?

I remember somewhere mentioned that posting dmidecode output publicly is risky (security/privacy).
53
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1answer
48k views

Why are the first 1024 ports restricted to the root user only?

This is more idle curiosity than anything else. A friend of mine asked me 'which port range is it that only root can use under Linux?' I told him 0-1024 were restricted. Then he asked my why it was so ...
5
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1answer
221 views

How do I know which files will be included in a linux kernel before I build it?

I am working on a project that includes building an old kernel version of linux. This is fine, but I still need to patch the kernel of all previously found security vulnerabilities based on CVEs. I ...
11
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2answers
3k views

How do I hide/anonymise/defend a computer when on hostile networks?

I connect to a lot of open networks when I'm pootling around. I'm fairly careful to VPN home for anything important but that's not really my boggle. The laptop runs several services (nfs, dev http ...
1
vote
1answer
2k views

How to secure CentOS and FreeBSD by disabling USB ports and VGA output on-site?

Is it possible to disable USB ports and CDRom and VGA output in the Dell R310 from CentOS or FreeBSD (without BIOS)? A demo server is running in a customer test laboratory, where they can simply get ...
3
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4answers
2k views

How to guarantee the integrity of an OS?

In information security, integrity means that data cannot be modified undetectably. This answer raised my interest, of course, I want to guarantee the integrity of my OS, outlined here. Suppose a ...
8
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1answer
2k views

Custom PAM modules and security considerations

I am writing my own PAM module that will be part of an application that I am developing, but I'm not sure exactly where to put it. My module basically does network-level authentication (with other ...
9
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3answers
4k views

How can I set that only root + a given user can shut down my pc?

If I'm using Ubuntu 11.04, how can I configure it such that that only two users can shut down/suspend/hibernate my PC: the root user and one regular user?
2
votes
1answer
2k views

How to create a “jailed” environment for an application under Linux?

Using Ubuntu 11.04 as a Desktop OS, I want to reach "bigger security" with a "jailing" processes: VirtualBox, Google Chrome, Firefox, VLC, PDF/djvu reader, MP3 player, wine, pidgin, transmission, ...
8
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1answer
2k views

Is /dev/random data a psuedo-random AES cypher, and where does the entropy come from?

My current understanding of an entropy pool is that it gathers truly random bits of data at a slow rate. I'd like to know how Unix & Linux collect entropy, and how that entropy is used by /dev/...
8
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2answers
4k views

Should I be backing up my SSH host keys?

In my automated backups, I'm not sure if I should be doing this. If the hard drive fails or if I wipe the hard disk and start over, what will be the effect of starting with a new SSH host key to my ...
1
vote
2answers
618 views

DNSSEC in the root zone? How to use it?

I'm using Fedora for desktop use and I: yum -y install caching-nameserver service named restart chkconfig --level 5 named on on it, and set the nameserver to 127.0.0.1. If I: dig google.com | grep ...
3
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1answer
2k views

Start X as a user other than root

I know some distro's (Moblin? ) have X starting as a user other than root already... What is required to do this? What steps need to be taken? I don't think it matters but I think X is started by KDM ...
-1
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1answer
5k views

What are the most secure cryptsetup parameters to create an Encrypted filesystem? [closed]

According to http://16s.us/Linux/dm-crypt.txt, it's better to use only dm-crypt, because LUKS leaves a trace. That's OK. But, what are the most secure cryptsetup parameters to use? E.g.: "aes-cbc-...
2
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1answer
504 views

What flags are used to compile debian stable packages?

Ubuntu wiki states that its packages are compiled with secure flags and secure kernel options. I cannot find this information about debian. See https://wiki.ubuntu.com/CompilerFlags
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3answers
120 views

Does PGPDesktop supports OpenBSD or e.g. Fedora?

Does PGPDesktop support OpenBSD or e.g. Fedora, or can I only encrypt my whole hard drive when I use Windows?
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2answers
2k views

nmap output: what does “uptime” mean?

If I nmap a host, then it outputs an "Uptime" too. What does it mean, is it trustable? Does it gives correct times?
2
votes
1answer
992 views

A local, centralized, secure way to store FTP login data, including passwords

I want to be able to store the login details all of my remote FTP accounts in one place, securely. Then I'd like clients like autofs/curlftpfs, Filezilla, etc to use this one store of passwords. I'm ...
6
votes
1answer
517 views

SSH tunnel with VNC?

In theory: I have a low-power consuption machine: eee pc, ok. I need to run a virtualized windows xp on it. (Because of a windows-only program..) I need to reach it from a smartphone (Android). The ...
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1answer
227 views

Linux user security

When a user is created in Linux, their username can be seen publicly in the passwd file. Is there a hash set for that?
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3answers
238 views

Tool to remove all non-package files on a system

If you want to keep for example a build or server system clean, it is very useful to be able to check that all files are present and accounted for by the package metadata. At work we have a very nice ...
3
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2answers
974 views

How to block outgoing connections from process/user on FreeBSD?

My server executes third party software which processes user submitted files. I want to block outgoing connections from my process. How can I do it in FreeBSD?
12
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4answers
2k 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
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5answers
166 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 ...
6
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1answer
4k 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 ...
9
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1answer
424 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 ...