Securing Linux systems and applications; understanding Linux security features.

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Why does Android use SELinux?

To restrict/sandbox processes Android uses SELinux. Why was that chosen and not the linux capabilities or cgroups+namespaces solution? After all the cgroups+namespaces is kind of home grown for them ...
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How to sandbox Iceweasel (Firefox) on Debian? [closed]

Are there any tools for sandboxing Iceweasel (Firefox) on Debian systems? I'm mostly interested in tools distributed by Debian. (An equally trustworthy source would be second best.) (I suppose that ...
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542 views

Process authentication for Linux

Is there any possibility to authenticate a running process in Linux to be sure that this is the original/right one? I know that an Linux operating system is only that secure like the way you use it. ...
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Breaking out of a strict linux sandbox running virtually under windows: do the linux-sandbox access control policies even matter?

I am developing an application which will run untrusted code. I have been designing it for linux, thinking that I can just run it in a virtual machine on windows when the need arises. The linux ...
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369 views

In Linux, when I consider trusting a new software source, what do I need to evaluate?

When I'm using the Linux software PackageKit, I get confused about what specific items of information I will need in order to decide whether to authorize software installation from a new software ...
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Is it possible to emulate real network printer i.e. to run some actual firmware in VM?

I've got to the section related to network printers exploitation while going through one security course. Under "network printer" I understand standalone devices with a dedicated ethernet\wireless ...
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What output can a program, when executed from a command line, output to generate behavior that is a vulnerability on the terminal emulator?

Reading this post, titled "Fixing Unix/Linux/POSIX filenames", I came across a VERY interesting phrase by the author, which says: Oh, and don’t display filenames. Filenames could contain control ...
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171 views

Prevent ARP spoofing with dynamic static entry on Linux

ARP spoofing detection/prevention seems to be quite popular here. With other techniques like port stealing aside, I'm wondering if the following could work to prevent it: Whenever my Linux ...
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1answer
294 views

Linux Plausibly Deniable File System

Is there any way to encrypt a linux filesystem in such a way to maintain plausible deniability? E.g. "Hidden OS support," the way Truecrypt and Veracrypt work, they only support Windows OS due to low ...
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Hacked Ubuntu server, probably hacked commands (netstat, ps, …), how to replace them? [duplicate]

An Ubuntu server of my company has been hacked to carry out a DoS attack. I found the shellshock bug had not been fixed by my colleagues, and I think it's the problem. Then, I found an ELF file that ...
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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. ...
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How to securely read a physical memory address in Linux?

I am trying to read a physical memory address in a device running embedded Linux with our application. The widely suggested method is to use mmap, convert it into virtual address and then read the ...
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Would running VMs inside of VMs be a more secure way to study viruses, etc?

I was reading this post on SuperUser, and it made me wonder about security. I've read somewhere else that some viruses/malware/whatever CAN break outside of a VM... and then infect the host OS. BUT, ...
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610 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 ...
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4answers
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Is GPG suitable as part of a password manager and generator?

I assume that GPG is very strong to crack, guess, etc. Since I have confidence in GPG, would it be appropriate to use my GPG key as the master key for a password manager or generator?
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What key does Linux use when storing user passwords?

Linux typically stores user names and password hashes in /etc/passwd or /etc/shadow. Now lets say I have an old CentOS distro and I want to attempt to recover a user's password (it's in a legal, ...
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Privilege Escalation Ubuntu

I am trying to learn how an attacker can escalate privileges in Ubuntu 10.04. I have heard that this can be done but no one has ever said how to do it. The best defense is knowing how it is done and ...
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Is privilege escalation possible when shell is under www user?

So, suppose that someone obtained a shell of a remote machine (of course via Internet). But the (linux) shell is under www user. Would there be any way of trying privilege escalation?
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buffer overflow attack scripts

I saw various different scripts for a buffer overflow attack. Many of the scripts include lines that look like this: char code[] = "\xdb\xd7\xd9\x74\x24\xf4\xb8\x79\xc4\x64\xb7\x33\xc9\xb1\x38" ...
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Phishing virus found on server

I recently had a call from BELL concerning a virus on our Linux ( Debian ) Server. Apparently Google emailed our client about an Italian Database found on our server that was doing phishing. They ...
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1answer
235 views

How is using acces() opening a security hole?

The man page for access(2) tells : Warning: Using access() to check if a user is authorized to, for example, open a file before actually doing so using open(2) creates a security hole, because the ...
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Can i compare linux user permissions without root access?

I've compromised two Linux user accounts on a RHEL machine (neither of which have root permissions) and I want to determine which account is more 'useful' to me in terms of access and privileges. Is ...
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538 views

How I can prove that SSH attacks are not from my application?

My ruby on rails web application is hosted on Linode. Linode opened a ticket and blamed my Linode server for attacking other servers. The logs revealed that it's a SSH brute force attack which ...
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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 ...
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511 views

How often is ASLR randomness refreshed, in Linux?

Most Linux distributions now use ASLR for many programs, to randomize the layout of memory. How often is the randomness used for this changed? If I re-run the same program multiple times, will it ...
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How to scan USB drive with clamav on Linux

Is there a way to scan the entire drive including auto-run and all partitions, including the master boot record (MBR)?
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Using TPM for full disc encryption?

E.g.: Can I make a better full disc encryption with e.g.: LUKS using the TPM? How?
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Where can I “hide” easter eggs for students learning about Linux security?

I feel like this isn't the best place to ask this (since there's no single right answer), but I can't think of a better place. If you have a better recommendation, could you please recommend it and I ...
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540 views

How a malware executes remote payload

Let's assume a malware was installed (on a UNIX-based platform) with some social engineering tricks. The original installed code itself may be benign, but the only malicious activity is that the ...
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Issues with preserving $HOME on sudo

On Ubuntu, the default behavior with sudo is to preserve the user's $HOME environment variable, which means that sudo will be able to read the dot files in the user's home directory. I enjoy this ...
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1answer
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Is there any security risk allowing regular Linux users to run arbitrary code?

I'd like to allow untrusted users to run arbitrary Node apps. If I use iptables to block everything except trusted servers, make each user's home folder only visible to them, and use runuser to start ...
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1answer
85 views

VirtualBox: Ubuntu With or Without Virtual Hard Drive

I've been working on a setup using VirtualBox that uses the Whonix Gateway as a Tor middlebox and I am planning on using Ubuntu for the workstation. I don't plan on storing any information on the ...
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262 views

Does the new Fedora package manager allow unauthorized installations?

I just upgraded to Fedora 22. The biggest change from the previous version is that the yum package manager is now replaced with dnf. One change I've noticed is that if you try to execute a command ...
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Security of LXC compared to OpenVZ

For years, I'm now using OpenVZ on my server, but support discontinued for Debian and Ubuntu, current releases seem to focus on LXC now, which is not a bad idea from the point of comfort. But what ...
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1answer
438 views

Testing a chroot environment for privilege escalation vulnerabilities

I'm looking for holes in my current implementation of a chroot jail that I have implemented for a group of users. Is there anything I can do better here? I utilized the following packages: RHEL6 ...
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1answer
117 views

GUI isolation in X11 when entering Truecrypt password

I have been getting a bit paranoid regarding some of my old TrueCrypt containers. The paranoia has got nothing to do with suspicions regarding TrueCrypt itself (after the shut-down last year), rather ...
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1answer
123 views

Automatically enumerate missing patches on penetration test

Nessus, when running a credentialed scan can check patch levels and return vulnerabilities when a package is one that hasn't been updated to the latest, non-vulnerable version. What is a good way of ...
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1answer
286 views

Are encryption keys wiped from RAM before hibernate, or how to do it (Luks and Truecrypt)

Using Linux, I have system and swap/hibernation partitions encrypted with LUKS, and data partitions encrypted with Truecrypt, and I am wondering when I put my laptop to hibernation if the encryption ...
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1answer
516 views

How to detect malicious code sending information to attacker's server in linux

Suppose you have some malicious code on your linux laptop, for example a rootkit or trojan or something like that. Now restrict your attention to the case that the malicious code does transfer some ...
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Is it better to use a root password, or use 'sudo bash'?

When I am doing a lot of sudo operations, I like to spawn a bash shell from sudo to make the operations go quicker. I am against assigning a root password because I do not like the root account ...
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How secure is it to keep the salt with the password hash? [duplicate]

In Linux we have the salt just next to the password hash in the /etc/shadows file. I always hear that salt value prevents hashed passwords from being cracked by brute force methods. But if somehow we ...
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software to keep a list of IP that try to access ssh over a set of rules and feasibility

i'm interested in software or set of scripts to keep a lists of filtered IP that attempt to brute-force ssh, and to label an IP as brute-forcing i would add some checks like: one attempt to log as ...
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3answers
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What are the risks of making ether-wake available to all users?

The Linux ether-wake utility, which creates a magic packet to wake on lan another machine, requires root access: $ether-wake 12:34:56:78:9A:BC ether-wake: This program must be run as root. To give ...
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2answers
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Can you describe a real-life scenario of exploiting sticky bits?

Sticky bit are mentioned in every UNIX security book, but I couldn't find anyone that describes the exploitation of Sticky Bit set on a file. Can you?
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635 views

How do I protect myself against the attacks in this php script?

Due to a vulnerability in how PHP was installed (Shared VPS with PHP installed as an Apache module instead of CGI) and hence how OSCommerce was configured (with security of 777 on certain ...
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5answers
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HOWTO : Email encryption in a browser

I have read about encryption and I think it's a good idea for me to encrypt my email. I run ubuntu 12.10 and use Firefox for browsing. In my quest for learning how to use gmail/hotmail to send and ...
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Making passwd/shadow files more secure

The passwd/shadow files in a unix-like OS contain sensitive info such as a user's password. In addition those files aren't necessarily secured: with a live CD we can access those files on the hard ...
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How to use VNC with SSH tunnel - “is this howto secure”?

PC-A: the local machine, from where i want to see the remote machine [Fedora] PC-B: the remote machine, where the vnc server will be [Ubuntu] install a vnc client [from where you want to connect] on ...
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Preventing Attacks Scanning for PHPMyAdmin etc

I have a Linux web server running Rails and each time I check the Nginx logs I find attempts to access PHPMyAdmin, database and admin directories such as this: 190.196.161.110 - - ...
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What are the security considerations for setting up a basic security testing environment?

I only have 2 spare machines and both are very old, but I really want to set up an environment so that I can start practicing security. One of these machines has a Pentium 4 processor and 512 MB RAM; ...