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

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24
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6answers
23k 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.
23
votes
5answers
2k views

How important is the sudo password?

I know that the sudo password protects my computer from being locally hacked by someone having physical access to it (edit : actually, it doesn't). My password is strong enough for that purpose, but I ...
23
votes
3answers
39k views

How to change LUKS passphrase?

Having installed Ubuntu 11.10 with whole disk encryption and LVM, I need to provide a way for users to easily change LUKS passphrase. Preferably, this should be done using GUI tools, thus, enabling ...
23
votes
3answers
2k views

What is the “Free software only” option when installing Ubuntu?

When installing Ubuntu, you get a Free software only option. Does that Free software only option mean Free as in beer or Free as in freedom? When I say free as in freedom, I mean FSF type of ...
23
votes
2answers
14k views

What is the 'ptrace_scope' workaround for Wine programs and are there any risks?

To run certain Windows programs in WINE you need to this workaround: echo 0|sudo tee /proc/sys/kernel/yama/ptrace_scope According to the support websites, this is due to a bug in the Ubuntu kernel ...
23
votes
3answers
2k views

What automated intrusion notification/detection setup is good for home desktop use?

I've been using Linux for quite a while now and I always feel the need to have a passive software / script setup which can alert me of any suspicious network activities like scans, failed login ...
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
2answers
8k views

What is the apt equivalent to “rpm -V” (Verify installed packages)

On a RedHat/CentOS system, I can verify the installed RPMs on my system using rpm -V. What is the Ubuntu or apt equivalent of this command?
22
votes
8answers
4k 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 ...
22
votes
2answers
546 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
7answers
1k views

How should a server be secured? [closed]

Talking towards Ubuntu 10.04, server edition, what tools/practices would you recommend to secure the server?
21
votes
2answers
1k views

How is the system kept secure?

I understand that if any malware made it's way into a Linux system, it will, at most, gain a user-level privilege and ruin anything within the particular user's reach, i.e. the user's own files. But ...
21
votes
2answers
5k views

How safe is Ubuntu? [closed]

Last week I started desktop sharing using krfb. Continuing from my last session, it appears that the process restarts itself. Two days ago I noticed messages popping up saying something like ...
21
votes
4answers
30k views

Which free VPN providers support Ubuntu?

Can't find any free VPN provider for Ubuntu. I tried looking into old questions but they seem to be outdated.
20
votes
2answers
7k views

Disable password access through SSH?

I'm setting up a server for backing up my desktop box remotely. I want to prevent remote password access to the server, permitting only users with private keys (AKA my desktop box) to access it. How ...
20
votes
5answers
8k views

Is there a preinstalled or automatic firewall?

Does Ubuntu come with a preinstalled or automatic firewall? If not, do I need one? I've read some articles about the advantages of linux over other operating systems about security (no need to have ...
20
votes
4answers
60k views

How to disable IPv6 permanently?

How can we disable IPv6 system wide via terminal commands? I've read editing /etc/modprobe.d/aliases and replacing: alias net-pf-10 ipv6 with: alias net-pf-10 off alias ipv6 off Is this safe ...
20
votes
5answers
14k views

Package denyhosts in Ubuntu Trusty Tahr is deleted: temporary or forever?

While doing a test-upgrade of our Ubuntu server to 14.04, I found that the package DenyHosts is no longer available. Installing it gives following error: apt-get install denyhosts Reading package ...
20
votes
2answers
14k views

How do I detect if someone is stealing my broadband bandwidth?

I am very paranoid about wireless connections and someone stealing my broadband bandwidth, which could lead to worse things. My question is, how can I detect if my broadband bandwidth is being ...
19
votes
3answers
7k views

Is this command to remove old kernels safe to use?

While browsing the internet for Ubuntu articles, I came across this command: sudo dpkg -l 'linux-*' | sed '/^ii/!d;/'"$(uname -r | sed "s/\(.*\)-\([^0-9]\+\)/\1/")"'/d;s/^[^ ]* [^ ]* \([^ ...
19
votes
2answers
13k views

Untrusted application launcher?

Some time ago, Ubuntu introduced a Security "feature", that would only allow trusted .desktop apps to be run, on other apps it would pop up a message. Nothing new so far, However, said Message used ...
19
votes
2answers
22k views

chkrootkit says /sbin/init is infected, what does that mean?

I recently ran chkrootkit and got the following line: Searching for Suckit rootkit... Warning: /sbin/init INFECTED What does this mean exactly? I heard this was a false positive, ...
19
votes
2answers
2k views

Why should I trust the “System program problem detected” dialog?

This always shows up a few minutes after I log in: I have no idea what it is. If I click Report problem, it asks for my password: This is exactly what I would do if I wanted to steal someone's ...
18
votes
7answers
3k views

What non malicious uses are there for ping's flood (-f) option? [closed]

I have been reading up on common ways in which people attack each other on the internet through things like DDOS attacks etc, and how one would defend oneself from such attacks, and I have come across ...
18
votes
9answers
15k views

Access Prompt keeps asking for GMail password

A pop up keeping appearing in Ubuntu (running 12.10), asking for the password to my gmail account. The icon has a silver shield, and it is labeled Access Prompt. The actual window has an image of ...
18
votes
3answers
4k views

Risks/Disadvantages associated with Wine

Can wine as a whole or the windows applications installed via wine pose some kind of risk to an Ubuntu installation? This question arose in my mind when I read this answer to my earlier question ...
17
votes
3answers
861 views

How can I force sudo to always ask for a password after waking from suspend?

Say I execute a command with sudo, then if I use sudo within the next 15/5 minutes (not sure how long it remembers me for) it won't prompt me for a password. It will only prompt me again if I haven't ...
17
votes
1answer
3k views

Update Manager does not ask for password anymore [duplicate]

I have realized this behaviour recently. Before that each time the update manager poped up to tell me there are updates and I tell it to install them it will ask me for a password. But since recently ...
17
votes
6answers
23k views

How can I audit users and access attempts to SSH on my server?

I've had a few security problems with a server of mine, a few SSH users have been setting up fires aka giving problems. I would like to: Track user logins and logouts Track activity of these SSH, ...
17
votes
2answers
906 views

Accidentally typed password in username input, any logs to clear?

I have accidentally typed my password in SSH's interactive username prompt. Are there any log files that I should clear?
16
votes
4answers
2k views

If I follow instruction from blog/web, is that always safe? [closed]

I am new with Linux especially Ubuntu. When I don't know how to do something with this OS I search on web and AskUbuntu and always have the answer. But sometimes it's not a great answer nor complete ...
16
votes
3answers
3k views

What's the difference if I use Windows 7 as a Standard User vs if I use ubuntu?

Ubuntu is secure for various reasons, one of them, a major one I believe, is that when you try to install a software/app via terminal/store an authentication box pops up asking you for your password. ...
16
votes
4answers
29k views

GUI for iptables?

I would like to secure my server and it seems that IPtables is one of the first steps. Unfortunately editing the rules in a terminal is a bit complicated and dangerous (those who ever did an iptables ...
16
votes
3answers
7k views

potential ufw and fail2ban conflicts

Will running both fail2ban and ufw cause problems? I noticed that fail2ban modifies iptables rules, but ufw already has a ton of iptables rules defined... so I'm not sure if fail2ban will mess these ...
16
votes
5answers
17k views

How to detect and remove a Linux trojan?

I recently (re)stumbled upon this: Linux Trojan Goes Unnoticed For Almost A Year (Unreal IRCd) Yes, I know that adding some random PPA/software from an untrusted source is asking for trouble (or ...
15
votes
2answers
4k views

New Zero-day exploit reportedly found affecting Linux/Android (CVE-2016-0728)

Russia Today reports (20 January 2016) that there is a new zero-day exploit that has been discovered affecting Linux and all Linux-based OSes for computers and phones. What is the deal; how does it ...
15
votes
2answers
2k views

Is it a bad idea to run SELinux and AppArmor at the same time?

My corporate policy says that Linux boxes must be secured with SELinux (so that a security auditor can check the 'yes, we're extremely secure!' checkbox for each server). I had hoped to take ...
15
votes
2answers
445 views

How can I further secure my system using 2 factor authentication?

The title pretty much says it. I have been hearing more about 2 factor authentication, one-time passwords, hard-tokens, and other improved security features. With the decreasing security of using just ...
15
votes
2answers
865 views

Does linux have a signature system for executables?

Windows has a signature system which allows you to make sure that an executable hasn't been modified after it has been signed. I used to use this as a security measure in Windows. Does linux have ...
14
votes
6answers
4k views

Does spyware exist for ubuntu?

Someone I know said he had put spyware on my computer. Is he talking crap? I've been using Ubuntu 12.04 for nearly 3 years now and I've never seen any type of spyware, remote keyloggers or RATS ...
14
votes
3answers
1k views

Unsupported Ubuntus - is it safe to continue with them?

I'll try to be as clear as I can about this, hoping to get clear answers. I have Ubuntu Studio 15.10, which is not an LTS version, and will only be supported till July 2016. Does that mean there ...
14
votes
6answers
28k views

How to secure ubuntu server from bruteforce ssh attacks?

I have my passwords secure, but I heard people complaining about perfomance of a server going down drastically when a bruteforce attack is taking place. How can I secure my ubuntu 10.10 server from ...
14
votes
6answers
12k views

Ubuntu One behind a proxy, how to make it work?

I am behind a web proxy server at work (no authentication) and I have set it up in Gnome (configuration applied system-wide). It works fine for accessing internet with a browser, but numerous ...
14
votes
3answers
2k views

Ubuntu vulnerable to malware sites?

I just browsed a site a while ago that was flagged as an "attack site" or has malware, but Firefox didn't warn before I went into it. Only when I opened a new tab with another page from the site did ...
14
votes
2answers
3k views

How can I tell that apparmor is working?

Some questions I want answered in the answer: How do I know if apparmor is running? How can I tell if it's working well?
14
votes
2answers
300 views

Should I include logs that contain “sensitive information”?

Sometimes, when info is being collected by ubuntu-bug (either automatically following a program crash or by manually calling it) the following dialog pops up: Should I include these files or not? ...
14
votes
2answers
612 views

How do I require Two Factor Authentication to log in?

Running 12.04. I am trying to separate my wrapped-passphrase for my encrypted home folder to require a USB drive be present to login. I followed the instructions here and added the drive to my ...
13
votes
1answer
707 views

In which country(s) is our Ubuntu One data stored?

In view of the UK government's new internet snooping proposals can anyone answer this question about the physical location of our data?
13
votes
1answer
32k views

What are ICMP redirects and should they be blocked?

After enabling ufw and the Tiger security auditor, I see warnings saying: The system accepts ICMP redirection messages What are ICMP redirection messages? Should they be disabled for security ...
13
votes
1answer
476 views

How to block specific apps from opening in specific accounts

How to block certain applications from opening on certain accounts (eg: Stop account John from opening Firefox or Gimp). It is assumed this is for the GUI and not the terminal and would only apply to ...