Securing Linux systems and applications; understanding Linux security features.

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Protecting data on a laptop with linux

I'd like to keep some private data (photos, notes, ...) and my browsing data hidden. The rest is not so important. Most of the time I just put the laptop to sleep and don't shut it down often, making ...
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3answers
458 views

Is it possible to USB whitelist in Linux?

After watching Black Hat's presentation on the fundamental problems with USB "security", I'm wondering if there's a way to do USB whitelisting in Linux. Is there currently a mechanism that will allow ...
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1k views

possible exploits through avahi daemon

It is always recommended to disable Avahi daemon, for security reasons, when not in use. So, by what ways it is possible to exploit a system which has avahi daemon service running? And how can we ...
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1k views

Impact of Mathew Garrett's Secure GRUB Bootloader on UEFI Secure Boot

My eyebrows rose with Matthew Garrett announcing his Secure GRUB Bootloader less than three hours after no longer being a Red Hat employee. This work and its impact on the trust chain design of the ...
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3answers
1k views

Restrict access to a specific directory on Linux

I want to limit access to a single directory on the hard disk (log files) to few processes (log files for a single process for example). All processes run under the same user, so file system access ...
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4answers
637 views

What mechanism enforces user permissions in Unix/Linux?

One of the core pieces of security in Unix/Linux systems is limiting privileges by user. For instance, certain actions can only be done by the root user. In theory, this can keep a malicious process ...
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2answers
856 views

Detect changes in /boot when using full disk encryption

When running a fully encrypted linux system using dm-crypt, the /boot partition has to be unencrypted to boot, as far as I know. I've setup a server that can be unlocked remotely by connecting to a ...
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1answer
5k views

what does it mean to be setuid root?

I am reading Tanenbaum's Modern Operating Systems 3e. He says "Suppose that the program being attacked [with malicious code] is SETUID root in UNIX (or has Administrator power in Windows). The ...
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1answer
6k views

Fail2Ban does not ban failed root login attempt

I have a small server which only open ports are ssh, http and https. I have fail2ban installed and set up so that after 3 failed attempts someone gets blocked for 10 minutes (thats the dafault I ...
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1answer
197 views

Does dual boot hurt security?

On my laptop I have a well secured Linux installation that I would like to stay this way. It has in the past and could in the future contain confidential medical data I use for my study. I also have a ...
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193 views

You've just acquired a newly created CentOS server, what should you do to secure it?

I've just acquired a new CentOS server, which will be hosting a Ruby on rails application, it is public facing. What should I do to secure this server?
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992 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 ...
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1answer
369 views

Exploited by newbie3viLc063s

My debian server got exploited by some scriptiekiddie who used Newbie3viLc063 http://pastebin.com/jma8JRG1 . Scriptkiddie uploaded logo_php.png to my server (My permissions sucked :s) and he did run ...
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1answer
2k views

What tools can be use for Security Auditing for Redhat

Are there any good tools that can be used for Security auditing of Redhat Linux. That can audit all the critical areas of System and provide the detailed output of all the audited sections.
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2answers
1k views

Restarting nginx with Jenkins or Phing - is it safe to allow Jenkins to run sudo without prompt for password

I am implementing the recommendations from Integrating PHP projects with Jenkins for my own PHP projects. I have created a jenkins user in my ubuntu 12.10 server. I used Phing as my build tool and I ...
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3answers
490 views

Security for home server, wiki

I recently set up my own home server, running Ubuntu linux. The intent I'm having for this is to have a private wiki for my family, so we can have a place to collect information like phone numbers, ...
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2answers
2k views

Can you have 2 promiscuous (sniffing) ports on a single machine?

I'm wondering if you can actually have 2 (or more) promiscuous (sniffing) ports on a single machine, to monitor multiple network segments? And can you monitor them all with snort?
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153 views

Do `sudo` and `su` belong to capability-based security?

In Linux, do sudo and su belong to Capability-based security ? For example, when editing a system file, we usually need sudo or su to temporarily switch to user root. Does this example belong to ...
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1answer
4k views

Is it safe to disable connection tracking in iptables?

While reading about NOTRACK target of raw table in iptables, I encountered an article suggesting that for certain traffic you could (or even should) disable connection tracking. The two examples were: ...
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532 views

Erasing encryption (LUKS) keys before suspend-to-RAM?

I recently had been wondering if there is a way to erase my LUKS keys from RAM before I suspend my device (usually a laptop) to S3 mode. I am interested in a solution that would work for my / ...
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1answer
246 views

Are we under hacker control?

We have a Web Server that mount Centos. Onto that WS there is an Apache (version 2.2.3) and some sites. You can log on only if you have a certificate (for root user) or via ftp (a restricted ...
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2answers
139 views

Can my /boot be compromised if I Suspend my notebook?

So if I use e.g.: LUKS, and I always suspend my notebook, then are there any methods to modify the unencrypted /boot? It contains the kernel! Or if someone tries (evil maid) to modify the /boot then ...
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2answers
254 views

What does a MCSE need to learn to be proficient regarding *nix security?

I have a top notch Windows MCSE/MCSD (developer) who wants to broaden his skills with Linux security... but needs to update his skills from the Ultrix / Yellowpages days of 40 years ago. What ...
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554 views

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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2answers
705 views

Executing arbitrary commands through iptables-restore input

During a pentest I found a way to add arbitrary iptables firewall rules to a server. These rules get applied by way of the iptables-restore command, and I've been wondering whether there is any way to ...
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1answer
709 views

Can auditd track events that occured over NFS

I have multiple servers mounting a NFS shared called /opt/WHATEVER from Server X. Server X has auditd enables with rule: sudo /sbin/auditctl -w /opt/WHATEVER -p rwxa When events occur on Server X ...
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1k 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 ...
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1answer
981 views

Firewall rules to block unwanted protocols on given ports

Does somebody has an idea, that what kind of iptables/pf rule must i use to achieve this?: i only want to allow these connections [on the output chain]: on port 53 output only allow udp - dns on ...
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2answers
213 views

Why was LibreSSL PRNG unsafe on Linux?

From the source: https://www.agwa.name/blog/post/libressls_prng_is_unsafe_on_linux The first version of LibreSSL portable, 2.0.0, was released a few days ago (followed soon after by 2.0.1). Despite ...
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1answer
312 views

Does Linux kernel use DEP for kernel memory?

Does the Linux kernel use DEP internally for its kernel memory? In other words, does the Linux kernel take care to ensure that, when the kernel is executing (in kernel mode), every executable ...
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2answers
446 views

How to improve VPS security?

I’m using Linux based VPS hosting, and a firewall and mod_sec help to keep most hackers out. However, over the last couple of weeks I noticed several entries in mod_sec showing that an unknown domain ...
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1answer
75 views

Is symlink race a very common vulnerability in UNIX systems

As far as I know, when I am creating a new file or directory in a directory that can be written by multiple users (and thus an adversary can have made a symlink there), the only way to protect myself ...
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1answer
31 views

What security problems does copying .Xauthority to another user present?

If I want to use a GUI application with another user (example: webbrowser), I can copy the .Xauthority file to that given user's home then I can "su - user" and start the GUI app. Question: but what ...
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1answer
112 views

Linux/ssh - Forensic question

In a Linux terminal, I made a ssh connection from A to B and I used commands to read some files stored in B. Then I disconnected and I closed the terminal. Is it possible to find on A, informations ...
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2answers
127 views

Is there a way to check for “hollow” processes, or malware hidden within “normal” processes

I recently came across an article on the The Verge, which centers around the concept of commercial malware production and how it's used around the world. The article introduced me to a number of ...
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705 views

What Ubuntu packages are still affected by gnutls bug CVE-2014-0092?

Right now the internet is abuzz with news about a severe breach in GnuTLS. An update to the relevant GnuTLS packages has already been released. But I am worried whether some packages might have had ...
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299 views

What would the cryptographic impact be of knowing the output of /dev/urandom?

Another noob question, I know, but something I'm unsure about. If I somehow magically knew the output of /dev/urandom at any given time, how much would that weaken a given encryption system? Or, ...
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4answers
840 views

does switching to linux remove existing computer virus

if you change from a malware/spyware infected windows setup to a linux setup will infections migrate to linux if they were on the computer? (when you are hacked/infected is it the op system that is ...
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846 views

Online security check via command line

My scenario is that I have a VPS with Apache (mostly for development of my own projects) accessed via SSH; and I time to time I would like to do a quick check just to be sure that there's no potential ...
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3answers
464 views

Best security practices for software development and release?

I am trying to figure out a way to limit access and also to establish processes to avoid any and all of my team members to compromise our entire production system. We have a team of 10 developers, 1 ...
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3answers
4k views

Besides OpenVas and Nessus, what are my other options for vulnerability detection?

I know of Nessus (which is $1300 for a pro feed) and OpenVAS (which I don't like). I use Linux so do I have any other options for vulnerability detection?
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5answers
2k views

Secure mount options + partitioning on Ubuntu

What is the best solution for mount options/partitioning when having e.g.: an Ubuntu minimal install (11.04) for Desktop use? e.g.: put /tmp on different partition to give it mount options like: ...
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1answer
1k views

How to remove ssh rootkits? [duplicate]

I checked my linux server with rkhunter, I got following warning messages, ... [00:35:35] Found file '/usr/include/gpm2.h'. Possible rootkit: Trojaned SSH daemon [00:35:35] ...
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3answers
277 views

Why should every file have a user and a group?

I've been reading in most hardening guides for linux, that you should check for files and directories without valid user or valid group. What I can't find, is how this could be used for an attack, or ...
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3answers
2k views

Disable Perl for some/most Linux users?

One of my server's web accounts got hacked a couple of times. Each time someone downloaded a Perl script via some phpBB forum and used the Perl script to do whatever they wanted to do (mostly connect ...
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1answer
1k views

Enterprise Anti-virus for Linux?

I know this question is probably at risk of offending the guidelines but our IaaS provider was unable to offer us an anti-virus solution for our Linux servers. We are deployed in an enterprise cloud ...
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3answers
132 views

Can the root of a system access to unencrypted data when using a double tunnel?

I connect to a DMZ gateway system (B) which is not secured. From this machine (B) I can connect to the final destination (C). A-->B-->C I created a ssh tunnel from A to B and forwarding the port 22 ...
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7k views

Decrypt from cipher text encrypted using RSA

I am sniffing a client side application traffic and I found some encrypted data. I am not able to decrypt it. Information which I have is Public Key: ...
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5answers
461 views

Blocking network access to host(s) at the kernel level in Linux?

Getting it out of the way: Not iptables! What I'd like to do is block network access to certain IPs, subnets, and/or hostnames at the Linux kernel level, such that no user, including root, could ...
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2answers
1k views

Securing a Ubuntu system on Amazon Web Services

I'm in the process of setting up a Ubuntu server on Amazon Web Services / EC2, which will need to host the following: A relatively simple Java-based website (using the Noir framework) A Java-based ...