Security covers a wide-ranging set of topics including Users, Permissions, Authentication, Authorisation, Upgrades, Firewalling, Hardening, etc.

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136
votes
6answers
101k views

How to patch the Heartbleed bug (CVE-2014-0160) in OpenSSL?

As of today, a bug in OpenSSL has been found affecting versions 1.0.1 through 1.0.1f (inclusive) and 1.0.2-beta. Since Ubuntu 12.04, we are all vulnerable to this bug. In order to patch this ...
132
votes
3answers
142k views

How do I patch/workaround SSLv3 POODLE vulnerability (CVE­-2014­-3566)?

After the BEAST attack and Heartbleed bug, now I've heard about a new vulnerability in SSL/TLS called POODLE. How do I protect myself against being exploited? Are only servers or also clients ...
128
votes
8answers
52k views

Are PPA's safe to add to my system and what are some “red flags” to watch out for?

I see a lot of interesting programs out there that can only be obtained by adding a "PPA" to the system but, if I'm understanding correctly, we should stay within the official "repositories" for ...
127
votes
5answers
91k views

What is the CVE-2014-6271 bash vulnerability (Shellshock) and how do I fix it?

Recently, there have been news going around regarding "CVE-2014-6271" (See USN-2362-1), which is a vulnerability in Bash. How do I know if I am affected by this, how can I fix it, and why should I ...
105
votes
6answers
71k views

How can I install just security updates from the command line?

sudo apt-get upgrade installs all updates, not just security updates. I know that I can use Update Manager to select only important security updates, but is there a way to do this from the command ...
84
votes
18answers
19k views

Why is it bad to login as root?

I've often come across posts on forums or other websites where you see people joking in such a manner about running/logging in as root as if it's something awful and everyone ought to know about it. ...
81
votes
8answers
43k views

How to delete file(s) in secure manner?

Is there a way to make sure that a deleted file can not be recovered? As you know, deleting a file by pressing shift-del or using trash doesn't mean that file is gone forever. It resides somewhere ...
60
votes
3answers
8k views

What is apparmor?

I hear a lot of talk about apparmor, I want to know the following: What is apparmor? How does apparmor work?
55
votes
8answers
26k views

What is the difference between “gksudo nautilus” and “sudo nautilus”?

I've been using gksudo nautilus and sudo nautilus through Alt+F2. What's the difference? They look very similar!
55
votes
1answer
6k views

Can I make the webcam take a picture when an incorrect password is entered?

I am using a laptop . I was thinking to have a support in my Ubuntu machine. When an incorrect password is entered, a picture is taken later revealing who has been trying to gain access. I have ...
51
votes
1answer
6k views

How to protect Ubuntu from fork bomb

I heard someone talking about a fork bomb, I did some research and found some dreadful information about some strange looking characters people can have you type at the command line and as a result do ...
49
votes
7answers
3k views

What are the risks of NOT using a firewall (home computer)?

Since a password is required to be a superuser (to install and modify programs), what are the risks to not use a firewall under Ubuntu ? More particularly if I am using a NAT router ?
48
votes
2answers
55k views

How do I keep track of failed SSH log-in attempts?

I'd like to see if somebody has been trying to log-in by brute-force into my Ubuntu 12.04 server over SSH. How can I see if such activities have been taking place?
48
votes
2answers
5k views

How can I use a passcode generator for authentication for remote logins?

I would like to strengthen the authentication of my SSH logins by adding another factor: a passcode generator device, or a passcode generation application on my mobile phone. The only obvious options ...
45
votes
10answers
30k views

How to harden an SSH server?

What measures can/should I take to make sure that security around my SSH server is absolutely impermeable? This will be community wiki from the start, so lets see what people does to secure their ...
45
votes
3answers
21k views

Difference between PGP and GPG

What are the main differences between PGP (Pretty Good Privacy) and GPG (GNU Privacy Guard) in relationship with security in Ubuntu and Launchpad?
44
votes
3answers
9k views

When to use pkexec vs. gksu/gksudo?

There are two general ways to run applications graphically as root (or, more generally, as another user). Programs like gksu, gksudo, and kdesudo are graphical frontends for sudo. In contrast, pkexec ...
43
votes
6answers
17k views

What is the best way to restrict access to adult content?

I bought my kids a PC and installed 12.04 (Unity) on it. The bottom line is, I want my children to use the computer unsupervised while I have confidence they cannot access anything inappropriate. ...
41
votes
2answers
18k views

Why shouldn't /var/www have chmod 777

When developing a page on a localhost, I sometimes get a "Permission denied" error which I can solve by running chmod -R 777 /var/www. However, people are telling me that this is a bad idea for ...
39
votes
7answers
11k views

What is the Ubuntu “built in virus protection”?

At ubuntu.com there is this "only in ubuntu" that says "Built in virus protection": What is the Ubuntu built it protection? What is the program in charge of this and how does it work?
38
votes
5answers
5k views

How can I prevent someone from resetting my password with a Live CD?

Recently one of my friends came over to my place, within 15 minutes he hacked my account using a Live CD and reset the password in front of me. I was baffled to see such a thing. Please guide me to ...
38
votes
5answers
53k views

Is there a way to password protect individual folders?

Let's say that I have a folder, within my Documents folder, that has files I want no one to access without a password. Is there a way to lock down that folder so that it's password protected / ...
37
votes
7answers
15k views

Why is Ubuntu more secure than Windows or Mac OS X?

Please give some solid reasons. Linked Question How safe is Ubuntu?
33
votes
4answers
11k views

Why is the firewall disabled by default?

Why is ufw firewall included in Ubuntu, when it is not enabled and pre-configured by default? Most users don't even know it is there, because no GUI frontend is provided.
31
votes
4answers
1k views

Does Ubuntu generally post timely security updates?

Concrete issue: The Oneiric nginx package is at version 1.0.5-1, released in July 2011 according to the changelog. The recent memory-disclosure vulnerability (advisory page, CVE-2012-1180, ...
31
votes
2answers
35k views

How to create a restricted SSH user for port forwarding?

ændrük suggested a reverse connection for getting an easy SSH connection with someone else (for remote help). For that to work, an additional user is needed to accept the connection. This user needs ...
31
votes
3answers
800 views

Is there any guarantee that software from Launchpad PPAs is free from viruses and backdoor threats?

As Linux continues to grow and develop, and the more we use Linux, the greater the threat from viruses. We also know that a virus/threat in Linux (if any) would have difficulty running or spreading ...
29
votes
8answers
12k views

How can I encrypt data in Ubuntu One or Dropbox?

I'd love to use Ubuntu One or Dropbox features, like file storage and so on, but I don't want anyone else to access my data, USA Patriot act etc.. I want things to be encrypted so that the only place ...
28
votes
14answers
10k views

Why is there no option to login as root?

Why does Ubuntu not allow the GUI users to login as root at the time of system start up like administrator in Windows? Why they are restricting us to login only through the terminal?
28
votes
7answers
1k views

What precautions should I take when exposing my desktop directly to the internet?

I've always used my Ubuntu desktop behind the security of a router with NAT, but there have been a few times when I've had to plug it directly into an active cable modem. In general, what precautions ...
28
votes
2answers
776 views

What precautions should I take with .debs I find on the internet?

So I was browsing the web the other day, and I came across a few places that wanted me to download .deb files - and since those are installed by root (and as such have the "powers" and capabilities of ...
28
votes
2answers
2k views

Should security updates always be installed?

We are a small shop, with no real sysadmin. So developers (Java EE) also try to maintain Ubuntu server 12.04. When I login a terminal and I see messages like: 6 packages can be updated. 6 updates ...
28
votes
8answers
9k views

How to set up a headless server?

I have a ubuntu development server at work. It is an old rack server that is located somewhere in the company's dungeon, where nobody ever goes. The only way it can work is as a so-called headless ...
27
votes
4answers
2k views

How do I configure Ubuntu for a public computer?

How would you set up Ubuntu on a computer that will be used as public computer in a library? I need the following features and user restrictions: On boot, a guest user should automatically be ...
27
votes
5answers
12k views

How to sandbox applications?

I want to run small untrusted programs, but restrict them from accessing any files outside of their folder, network access, and everything else that they don't really need. What is the simplest way to ...
26
votes
8answers
3k views

What do I have to do before giving away my Ubuntu machine?

I have an old laptop that is running Ubuntu. Now I want to give away this laptop, but I want to remove all private data. So what should I remove? I don't want to format the whole system, because the ...
26
votes
5answers
7k views

What if I run a virus/trojan Windows EXE on Ubuntu with Wine?

I've got a file said to contain information I was looking for. Unfortunately it is an executable instead of DOC (as it was meant to be) and the site I've download it from looks suspicious for me. If I ...
26
votes
1answer
1k views

How to find my lost Ubuntu laptop?

I am running Ubuntu on my laptop. In case if I lose my laptop or it gets stolen, is there any way to locate it? Do I have to install any application beforehand to find my laptop?
26
votes
1answer
1k views

How to know if a authenticate box is real or fake?

For example, someone creates a fake Authenticate dialog to get my root password. How to know if it is real or fake?
25
votes
17answers
21k views

Can you recommend a password generator?

I was hoping someone could recommend a good password generator. Extra props to the person who can name one that gives you a mnemonic to remember it as well.
25
votes
5answers
5k views

What's wrong with using sudo?

In a comment here I've been told that unnecessarily using sudo should be avoided. While it wasn't needed in that particular case, I don't see any harm in using it. I think that when executing trivial ...
25
votes
7answers
13k views

Basic Ubuntu FTP Server

I would like to setup a basic FTP server on my Ubuntu Server install. I have been playing with VSFTPD, but am having issues getting the server to allow me to create directories and copy files. I ...
23
votes
6answers
2k views

How can I confirm that the binaries in my Ubuntu are from the source code it should be from?

Like 99% of users, I install Ubuntu from ready-made binaries. How can I verify myself that those binaries are in fact from the original source code from Ubuntu? It would be good to verify that ...
23
votes
3answers
35k views

How do I setup OpenVPN so I can securely use the internet from an unsecured hotspot?

Goal: I want to be able to securely use the internet via my home PC while my notebook is connected to an open hotspot/access point. I do know that I can use a SSH tunnel/SOCKS proxy, but I don't want ...
22
votes
1answer
1k views

Is Ubuntu vulnerable to recent exploits using USB sticks and automount?

I read recently that someone demonstrated a security attack on a PC via the use of automount and a USB stick. How vulnerable am I to this attack and what steps are developers doing to be proactive ...
22
votes
4answers
17k views

How can I detect a keylogger on my system?

How could I know if there's a keylogger in my system, or at least if one is active right now?
21
votes
6answers
17k views

What Can Be Done To Secure Ubuntu Server?

I have a project to secure Ubuntu Server as much as I can. The server is a web hosting server. The server will be running LAMP , Mail , and DNS.
21
votes
8answers
3k views

Where can I look for malware that may have been installed on my machine?

I want to analyze my ubuntu box to detect if it was been hacked. My question is: what are all the place where to look to discover if some malicious software are started ? The following is some kind of ...
21
votes
2answers
447 views

Is the meta-release upgrade (do-release-upgrade) secure?

I am trying to understand the do-release-upgrade process i.e. the way that Ubuntu prompts me to upgrade to the next spring or autumn Ubuntu release. After reading the sources for ...
21
votes
1answer
71k views

How do I scan for viruses with ClamAV?

I installed ClamAV via Terminal (Ctrl+Alt+T) with: sudo apt-get install clamav but how can I scan for viruses?