Securing Linux systems and applications; understanding Linux security features.

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90
votes
3answers
15k views

Is a rand from /dev/urandom secure for a login key?

Lets say I want to create a cookie for a user. Would simply generating a 1024 bit string by using /dev/urandom, and checking if it already exists (looping until I get a unique one) suffice? Or should ...
67
votes
9answers
13k views

Hardening Linux Server

We have already had questions on here about Hardening Apache, Hardening PHP and Securing SSH. To continue this trend I am interested in what steps people take to harden Linux servers. As in what ...
186
votes
5answers
110k views

What is a specific example of how the Shellshock Bash bug could be exploited?

I read some articles (article1, article2, article3, article4) about the Shellshock Bash bug (CVE-2014-6271 reported Sep 24, 2014) and have a general idea of what the vulnerability is and how it could ...
24
votes
6answers
10k views

How to prevent BadUSB attacks on linux desktop

What can I do to protect my linux laptop from BadUSB attacks as described here? Perhaps writing an appropriate apparmor profile would help?
26
votes
4answers
23k views

What can an attacker do with Bluetooth and how should it be mitigated?

What are the security risks of Bluetooth and what technologies and best practices should be used to protect my device? What can an attacker do once a malicious device is paired with mine? ...
32
votes
6answers
5k views

Secure Linux Desktop

I'm looking for hints about secure linux desktops. Securing servers is no problem. Most recent Software Updates, run only the services required etc. But what about desktops? I'm thinking about details ...
7
votes
7answers
3k views

Server compromised for 2nd time, cannot locate source of attack

I need some help tracing a vulnerability on my server. For the second time, my server has been compromised with files being replaced with virus-ridden downloads. According to the filesystem dates, ...
106
votes
8answers
6k views

Attacking an office printer?

I did an nmap scan on an advanced office printer that has a domain name and is accessible from outside the corporate network. Surprisingly I found many open ports like http:80, https:443, and ...
28
votes
4answers
21k views

How do you know your server has been compromised?

I recently helped a client who had their server hacked. The hackers added some PHP code into the header of the homepage redirecting the user to a porn website — but only if they came from Google. This ...
17
votes
1answer
17k views

Configure SSL Mutual (Two-way) Authentication

A lot of tutorials, a lot of pages, a lot of question and they differ in implementation of this issue "Configure SSL Mutual (Two-way) Authentication". I have to do it with Linux, and I don't know from ...
8
votes
4answers
9k views

Monitoring system calls (in a reliable and secure way)

It there a reliable method of “monitoring” system calls under Linux? There is strace for example to monitor system calls and signals. Is there a way for a process to dodge out of strace? If yes, is ...
7
votes
2answers
470 views

What features do you look for in an Enterprise Log Management solution?

This question is for IT Pros, and people who manage a company's infrastructure. Developers should see this related answer for tools geared for them. What are your requirements for such a Event Log ...
-2
votes
1answer
1k views

Cascading Encryption Algorithm using mcrypt or GnuGP

I'm trying to a cascading cipher encryption algorithm to encrypt a textfile via mcrypt. I'm essentially trying to emulate the behavior of TrueCrypt, where it can cascade two or three different cipher ...
39
votes
3answers
78k views

What is the difference between authorized_key and known_host file for SSH?

I am learning basics of SSH protocol. I am confused between the contents of the following 2 files: ~/.ssh/authorized_keys: Holds a list of authorized public keys for servers. When the client ...
38
votes
4answers
22k views

Should I get an antivirus for Ubuntu?

Considering the recent thread regarding anti-virus for the Mac I wonder how many of the arguments put forth are relevant today to Linux systems, specifically Ubuntu. There are no known Ubuntu ...
12
votes
8answers
8k views

How anonymous is my setup?

my friend and I are trying to make the most anonymous setup for a computer to do things across the internet without being known the location from which it came. Our setup is as follows: A windows ...
17
votes
7answers
6k views

Any comprehensive solutions for binary code protection and anti-reverse-engineering? [closed]

Does anyone know of good products with comprehensive binary hardening and anti-reverse-engineering features? Or better, has anyone seen an independent review comparing products that perform these ...
12
votes
3answers
4k views

Using TPM with DMcrypt?

Is it possible to use TPM for storage of some private key? It's not a full-disk encryption , I want it to be compatible with existing LUKS, just add another key, and store it in the TPM.
12
votes
6answers
1k views

Securely building a local pentest lab in a VM

I'd like to set up OWASP WebGoat or a similar vulnerable web app in a VM (probably VirtualBox on Linux). For convenience's sake, I'd like to get it running on one of the primary machines I use (say, a ...
18
votes
0answers
606 views

Where can I find a vulnerable operating system to practice pentests on? [duplicate]

I am looking for vulnerable operating systems that are used for practicing pentests. Damn Vulnerable Linux (DVL) is not maintained anymore. Are there any other simillar OS´s to download somewhere that ...
30
votes
3answers
27k views

Simple example auditd configuration?

Auditd was recommended in an answer to Linux command logging? The default install on Ubuntu seems to barely log anything. There are several examples that come with it (capp.rules, nispom.rules, ...
37
votes
9answers
4k views

Is full disk encryption on a server in a secure data center pointless?

I am having a debate with several people regarding how much protection full disk encryption provides. dm-crypt is being used to encrypt data which is required by my company to be encrypted at rest. ...
13
votes
5answers
8k views

Linux command logging?

Recently someone broke into one of our linux servers as a non root user. An excerpt from .bash_history: [...] perl perl set +o history set +o history set +o history passwd sdfsdf passwd exit I ...
15
votes
2answers
3k views

Security Concerns with X11 Forwarding

What are some of the security concerns and reasons either for or against allowing X11 Forwarding. I have generally taken an approach of not allowing it under the blanket guise of security. Recently, ...
11
votes
2answers
6k views

For LUKS: The most preferable and safest cipher?

I'm about to encrypt two of my hard drives using LUKS, since I can't really do it myself I use the guide on the Arch Linux wiki (which can be found here). In an example in the guide the cipher ...
8
votes
7answers
5k views

Linux or Windows- the security issue [duplicate]

Possible Duplicate: Open Source vs Closed Source Systems Almost anyone who has grown up on Windows must have had the notion (that I had) of Linux being more secure than Windows- one of ...
9
votes
2answers
11k views

Is it possible to use the aircrack-ng tool to crack a WPA2 Enterprise network?

is this tool (aircrack-ng) capable of cracking into a WPA/WPA2 Enterprise network? This tool has major success cracking the passwords of WEP/WPA networks. If it can, how, but if not, is there another ...
8
votes
5answers
2k views

How can I remotely wipe the contents of a Linux Laptop if its been stolen?

I am currently investigating using Linux Laptops for my development team. We currently run Windows. The one advantage that keeps coming up for Windows over Linux from a system administration / ...
7
votes
2answers
611 views

Is there any Linux distro or kernel patch that wipes a process memory space after the process exits?

An application runs on an embedded battery-powered PC, accessible to some restricted public, that stores secrets in RAM. To prevent cold boot attacks and that the PC is stolen to extract its secrets, ...
6
votes
2answers
2k views

Escalating from Apache shell to root

I have one noob question.I tried to exploit shellshock on my Slackware linux server, but after I connect with reverse shell and User Agent I get that I am apache user and apache user don't have too ...
6
votes
3answers
566 views

Appropriate defense for 404s in my logs - persistent web scans from one region

This seems to be a fairly easy question to figure out, but I wanted to make sure. I've got about a thousand entries on one of my web servers with phpmyadmin in the connection criterion, but as I ...
1
vote
4answers
14k views

Netcat IP Spoofing

I am connecting to a server nc -v 192.168.0.1 1111 But I want to do IP spoofing because the server on 192.168.0.1 only accepting commands from 7.7.7.7. We are two friends, I am 192.168.1.1, and my ...
0
votes
0answers
115 views

Improve the security of a website implementing the least privilege principle

I am a beginner and I am trying to program a secure website to improve my skills and knowledge. I am under Linux and I am using LAMP with php. My website is similar to a social network so people will ...
9
votes
4answers
4k views

How to disable Firewire in OpenBSD/Linux to prevent attacks through Firewire?

Since Firewire lacks security, allowing a plugged-in device to access host memory, it's a good thing to fully disable it. If we're not using the BIOS to disable the Firewire port then how could we do ...
6
votes
1answer
2k views

Using TPM for full disc encryption?

E.g.: Can I make a better full disc encryption with e.g.: LUKS using the TPM? How?
2
votes
1answer
65 views

Diffie Hellman parameters still calculating after 24 hours

I have a fresh install of Arch Linux on a RaspberryPi model B. I'm setting up OpenVPN and using easy-rsa with OpenSSL 1.0.2d to generate initial keys and certificates. All went fine until I ran ...
2
votes
2answers
2k views

Is user password in ubuntu 13.04 in plain text?

Is it stored in plain text or not? Where can I find the file that contains the username and password for my accounts in Ubuntu 13.04?
1
vote
2answers
548 views

How to change default cipher in GnuPG on both Linux and Windows?

How can I change the default symmetric cipher used by GnuPG from CAST5 to another? I'm using GPG4Win on Windows, but would also be interested in a solution for Linux.
1
vote
3answers
341 views

Removing a Redirect Virus from Fedora Linux

Despite several attempts listed below certain websites are getting redirected to a certain ad website automatically, out of the blue on linux. When some website starts redirecting to this ad website ...
1
vote
2answers
145 views

Open Source OS - code you see vs code you get

In this question I will use the example of Linux OS, but I am also interested in general situation. Linux OS distributions are famous for being open source and thus rather secure. But how can you be ...
1
vote
3answers
408 views

Cracking passwords after a pattern with John

So I am trying to find out how easy it is to crack a password using some great Linux tools. We all know about John as a password cracker and how great it is. But how about specifying a pattern. ...
51
votes
7answers
5k views

Can “cat-ing” a file be a potential security risk?

I often use cat on the console to view the contents of files, and every now and then I accidentally cat a binary file which basically produces gibberish and system beeps. However today I've ...
33
votes
6answers
7k views

Keeping secrets from root on Linux

I am looking for ways to harden a linux system so that even when gaining full root access (through legit or non-legit means), some secrets remain inaccessible. But first a little background. Many of ...
42
votes
7answers
9k views

Should I change the default SSH port on linux servers?

Is there any advantage in changing the SSH port, I've seen people do that, but I can't seem to find the reason why. If you have a strong password and/or a certificate, is it useful for anything? ...
14
votes
4answers
3k views

environment variable accessibility in Linux

Perhaps this is a trivial question, but how accessible are environment variables in Linux between different users? e.g. if Alice executes export FAVORITE_FOOD=`cat /home/alice/fav_food.txt` Can ...
5
votes
2answers
6k views

How to secure a dedicated linux server running a LAMP stack for commercial E-commerce use

To be more specific, I would like to get some help, either through a tutorial or through a book, on how to configure an apache server to run securely and minimize the risks for commercial use. ...
14
votes
3answers
2k views

VPS security best practice

I've just signed up for a linux VPS to host a website I've been creating and I need some advice on the best approach to secure it. I've previously been hosting it off a VM in the house, but I want to ...
17
votes
3answers
2k views

Why doesn't Linux randomize the address of the executable code segment?

I've recently been learning about how ASLR (address space randomization) works on Linux. At least on Fedora and Red Hat Enterprise Linux, there are two kinds of executable programs: Position ...
12
votes
2answers
5k views

Available Resources for Securing RHEL 6

Some in our infrastructure group want to upgrade to start taking advantage of the new features in RHEL 6. In the past, I have relied on the NSA Guide to secure RHEL 5 and CentOS 5 installations. I ...
6
votes
7answers
7k views

Physical computer security, how to disable USB ports when the computer is 'locked'?

Lets say my PC & server is in an environment where a theoretical attacker has physical access to the machine while I'm not there. Now the data is encrypted on the hard drive with TrueCrypt. ...