Ask Ubuntu
Ask Ubuntu

Questions tagged [security]

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

Ubuntu has many Security Features, and a Security Team dedicated to keeping users safe and up to date. Please feel free to get involved, or read through the Ubuntu Security FAQ.

2544 questions
409
votes
10 answers

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 line?
crenshaw-dev
  • 32,852
345
votes
9 answers

Are PPAs 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 adding software to our system. Is there any way for a…
Rob
  • 12,940
246
votes
11 answers

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 in the computer. In day to day life, law…
user20296
226
votes
22 answers

Why is it bad to log in 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. However, there isn't much that a search reveals on…
Mussnoon
  • 5,236
225
votes
2 answers

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?
BuZZ-dEE
  • 14,533
175
votes
3 answers

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?
Luis Alvarado
  • 216,643
175
votes
2 answers

Installing python: who is deadsnakes and why should I trust them?

I want to install Python 3.9 on my Ubuntu 20.04, and all tutorials I can find include a step as follows: sudo add-apt-repository ppa:deadsnakes/ppa I am concerned about security. I've looked into this question: Are PPAs safe to add to my system and…
Pedro A
  • 1,963
158
votes
4 answers

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 affected? Is this OpenSSL/GnuTLS specific? What kind of…
gertvdijk
  • 69,427
153
votes
6 answers

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 vulnerability, affected users should update to OpenSSL…
Lucio
  • 19,191
  • 32
  • 112
  • 191
146
votes
3 answers

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 to be able to forward his port through the server…
Lekensteyn
  • 178,446
142
votes
5 answers

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 care? This is designed as a canonical answer for…
nanofarad
  • 20,906
141
votes
3 answers

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?
Ivan
  • 58,745
135
votes
13 answers

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 do to secure their servers.
LasseLuttermann
  • 14,913
133
votes
2 answers

How can I allow SSH password authentication from only certain IP addresses?

I'd like to allow SSH password authentication from only a certain subnet. I see the option to disallow it globally in /etc/ssh/sshd_config: # Change to no to disable tunnelled clear text passwords #PasswordAuthentication yes Is there a way to apply…
ændrük
  • 78,496
110
votes
7 answers

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!
DrKenobi
  • 6,552
1
2 3
…
99 100