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

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1answer
10 views

My security it's vulnerable, 3 passwords changed in one week

What i have to do in this case, i have my security updated but can't give me if some one trying access me. This week i was hacked 3 times, i'm attest in that times, and if not. What i have to do ...
0
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0answers
9 views

How i can do for know what i have to do i this type of cases: root?

i receive that message when i want install or try to don know that was installed, after it's here : apt-get install linux-generic -(the error)- E: Could not open lock file /var/lib/dpkg/lock - open ...
4
votes
4answers
40 views

How does FDE (Full Disk Encryption) work so quickly?

I'm curious about how does Ubuntu's full disk encryption works under the hood. Here's an example: Considering the following string as all the disk's content: hello world After applying some kind ...
3
votes
1answer
27 views
+100

How to ensure user separation on an old school shell server

I want to run an old school shell server for a couple of people, ie. one where users get ssh access so they can run software (their own or provided). My concern is appropriate separation between ...
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0answers
26 views

Are Ubuntu based distros as secure as official ones?

I'm taking about distros like mint, deepin, elemantry, ... Do these get updates just like official Ubuntu?! How about security modules like selinux and apparmor ?! Are they included ?! What about ...
12
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4answers
3k views

Personal computer hacked: How do I block this user from logging in again? How do I find out how they are logging in?

I am 99.9% sure that my system on my personal computer has been infiltrated. Allow me to first give my reasoning so the situation will be clear: Rough timeline of suspicious activity and subsequent ...
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0answers
18 views

We have installed Suricata on our system so we have the following similar lines in our fast.log, can anyone explain these lines

03/17/2016-17:18:52.744707 [**] [1:2200075:1] SURICATA UDPv4 invalid checksum [**] [Classification: (null)] [Priority: 3] {UDP} 193.11.188.181:5353 -> 224.0.0.251:5353 03/17/2016-18:21:25.046125 ...
75
votes
11answers
76k 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 do to secure their ...
2
votes
2answers
1k views

verifiying ubuntu iso with repository gpg-keys

I want to verify that a downloaded ISO is not being poisoned by the NSA or any other immoral agent. To do this I would very much use a signing-checking way. I am aware of VerifyIsoHowto. Still I am ...
14
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1answer
34k 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 ...
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0answers
17 views

EFI blocking Dual Boot Kali Linux? [on hold]

Just now i was trying to dual boot Kali Linux with my newly upgraded windows 10 (from windows 8.1). So i made my bootable USB from PowerISO and when i entered BIOS to choose my drive to boot into , ...
1
vote
1answer
31 views

How to use SSL and SASL with irssi under Xenial Xerus?

I would like to connect to Freenode with irssi using both SSL and SASL. Instructions for using the script cap_sasl.pl that worked for older versions of irssi now show the following error under Xenial ...
1
vote
1answer
15 views

How can I encrypt my pendrive with password? [duplicate]

In windows 7 or windows 8, I can use BitLocker Drive Encryption to encrypt and set a password in my pendrive but i am unable to access files of my pendrive in Ubuntu. Is there is any method to ...
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3answers
266 views

Should the root / have 777 permission?

Most of the contents is 755 though. Is this a problem?
3
votes
1answer
573 views

ClamTK Anti Virus will not run on Ubuntu 15.10

I have a laptop running Ubuntu 15.10. To protect myself, I have tried downloading and installing ClamTK. It does this without giving any error messages but it doesn't open. I tried on a second ...
2
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4answers
144 views

Is there any way to verify a Ubuntu iso or hashsum?

Neither the iso nor the hashsum is available via https. Is there any way to verify you're not getting man-in-the-middled?
1
vote
0answers
15 views

shutdown or reboot after entering wrong password x times

My laptop is configured with a bios password to unlock the encrypted ssd. Most times I don't shut it down and use just suspend/resume - this of course leaves the ssd accessible. To increase security ...
-5
votes
1answer
145 views

Ubuntu LTS 16.04 – Security – Code-Review [on hold]

Just installed the new Longterm Version. Since I'm new in the Ubuntu world, I was a bit shocked what is going on "in the year 3 after Snowden". So here are my questions: How can I delete (realy ...
0
votes
1answer
29 views

Does posting my computer name publicly make my system vulnerable?

I am wondering if it is paranoia and/or privacy overkill to block out one's computer name when posting terminal output in public forums? I don't know enough about networking to know if it's possible ...
0
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2answers
155 views

Kernel live-patching in kernel 4?

According to Linux 4 release documentation, live-patching of kernel code is now possible in Linux 4. Does Ubuntu 15.10 Wily support these live in-RAM patches without rebooting? Do I need to do ...
1
vote
1answer
76 views

Is Ubuntu 16.04's Snap format secure?

A recent leak claims that Ubuntu's new Snap Format is not secure - http://news.softpedia.com/news/developer-claims-that-canonical-s-new-snap-format-isn-t-secure-on-ubuntu-desktop-503287.shtml. Since ...
4
votes
1answer
19 views

How can i find that which file was copied from my pendrive last time?

I forget my pendrive in my office. I have doubt that someone copies my important documents and files from my pendrive. Is there any method to find that which file is copied from my pen-drive? Please ...
0
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0answers
16 views

How to trigger lock-screen on visiting a website?

The website in question is my Google Drive. I have many confidential data in my Google Drive. And my google account is signed in on my laptop. Also I tend to leave it unattended at times. I want to ...
0
votes
1answer
25 views

Secure way of geting checksum

I was just wondering, is there any way of how to securely get checksum from major branches of ubuntu? As a general rule I do not trust anything that can be easily manipulated for that I do not believe ...
0
votes
1answer
25 views

How to detect screenshots in Ubuntu?

Apart from monitoring keystrokes for Print Screen, is there a way for a tool or software running in Ubuntu (whatever the desktop) to detect that a screenshot or video recording of the whole or a part ...
0
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3answers
379 views

What does this “find” command do?

I am so beginner on Linux and I have run the following command while I am on /root: find . -type d -exec chmod 770 {} \; && find . -type f -exec chmod 660 {} \ I meant to run that on a ...
2
votes
1answer
20 views

Is choosing 'Security Updates Only' on installation of Ubuntu Server enough?

I want necessary security updates on my Ubuntu servers, without my interference. In general, do I need to do anything else after selecting the 'Security updates only' option in the automatic updates ...
0
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0answers
14 views

Ubuntu Touch - Screen locking fade issue

On my Ubuntu phone, I have set my screen lock to come on after a minute of none use. This is in the Settings > Security & Privacy > Locking & Unlocking. The lock does come on as requested ...
0
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2answers
16 views

Regular security checks on server

I am administrating a server and obviously i am slightly paranoid if its security is compromised. Hence i regularly try to check if the security is still intact. Here are the things that i do roughly ...
-2
votes
0answers
22 views

error !!configuring Linux-image-4.2.0-35 generic

I want to install Ubuntu on a new HDD.when configuring Linux-image-4.2.0-35 generic, prompted security freeze lock.the system can not be installed
8
votes
2answers
2k views

What is the 'Badlock Bug'?

A user on the Ask Ubuntu General Room posted a link to Badlock. After some googling around, all I can find is that it is a mysterious security bug, that uses the same website template as Heartbleed. ...
5
votes
1answer
14k views

Ubuntu - saying your security settings have blocked an application from running with an out-of-date version of java

I have this new problem since 2014 begin. I cant remotely login to this enterprise network for giving them support. Its keep showing this new error. How to fix it please? EDIT:
10
votes
1answer
269 views

How to prevent users from changing their password to one of the last X passwords?

I have an Ubuntu GNOME 15.10 with GNOME 3.18 system which I would like to set up so that the users using it cannot set a new password as one of the previous X passwords, how can this be achieved? ...
5
votes
1answer
919 views

Prevent Skype resolvers getting your IP on Ubuntu

I am running Skype version 4.3.0.37 on Ubuntu 14.10, and I know that on the Windows version there is an option to only allow direct connections to your machine through Skype for Skype contacts, which ...
0
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0answers
11 views

lxcbr0 stop container communication

I'm creating LXC containers to be used by different users but required each container to connect to lxcbr0 to provide remote access. How can I restrict with LXC that containers on a default bridge ...
0
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0answers
11 views

Evaluating URL Whitelists for Security Threats

I have a very long list of URLs to whitelist on my Ubuntu Squid proxy. I have looked through this list that was provided by another group and there are sites in the list that seem to range from ...
9
votes
1answer
2k views

Are all versions of Ubuntu secure against DROWN attack?

OpenSSL updates release versions 1.0.2g and 1.0.1s to fix the DROWN vulnerability (CVE-2016-0800). In Ubuntu 14.04 LTS Trusty Tahr, the latest OpenSSL version is 1.0.1f-1ubuntu2.18. Do I understand it ...
2
votes
1answer
460 views

What do I do about Badlock on Ubuntu 14? [duplicate]

So, the Badlock bug (www.badlock.org) that was revealed yesterday, was not as terrible as feared. And yet, it seems prudent to patch samba ASAP. However, just prior to releasing the bug, the samba ...
11
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2answers
4k views

What is the name of the security concept that explains why Linux asks for root password?

Whenever I'm installing new software or making changes to the system, Linux asks for the root password. What is the name of this security concept and where can I research more information about it?
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0answers
15 views

Restrict user to run only one program with Wine

I want install Wine and Picasa for an user. I want prevent the user from running *.exe-Files basically for security reasons. In the past (bevor 3-4 years, another Ubuntu-Installation) I discovered, ...
4
votes
0answers
43 views

Is the lock screen secure?

I have a fully encrypted drive so I know when my laptop is turned off that nobody can access my data but what about when the screen is locked with my root password? It is often impractical to turn ...
11
votes
2answers
4k views

Yubikey Two-factor Authentication Full-disk Encryption via LUKS

I recently acquired a Yubikey Neo - a nifty little hardware second factor authentication device. It's primarily intended for use with One Time Passwords, and the emerging U2F protocol - but since ...
0
votes
1answer
49 views

File/folder protection that even government cannot break [closed]

If I have some intellectual property file that under no circumstances my competition can view, what is the best and most secure way to protect them? I know that there are many encryption apps for ...
3
votes
1answer
67 views

is the current Adobe Flash 'ransomware vulnerability' affecting Ubuntu users?

Currently there is an important release from Adobe telling users to update their Flash after learning of certain vulnerabilities where users computer are infected with ransomware. One of the many news ...
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0answers
19 views

Ubuntu Vulnerabilities Filtered By Severity

It there a page that provides a list of Ubuntu security vulnerabilities by priority? The CVE Tracker seems to be colour coded by priority but I'm looking for something that I can easily filter based ...
0
votes
1answer
24 views

Permission denied for ubuntu shell user to list home directories of users

When I use shell I can't list the directories of local home users created by useradd or through virtual min ls -ls /home/someuser/ permission denied but I can list directories created by root. ...
3
votes
1answer
73 views

Do malicious web sites ever exploit vulnerabilities in Linux clients? [closed]

Do malicious web sites ever exploit vulnerabilities in Linux clients? Are there any documented instances of this happening in the wild? I am talking about actually taking over the client's machine ...
17
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2answers
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 ...
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votes
2answers
141 views

What are the alternative to clamtk

I installed the antivirus clamtk/clamav, the installion went well, but I can't run the program. I tried a terminal, but that did not work. The result was if I typed sudo clamtk nothing happen, but if ...
-2
votes
1answer
51 views

Fix duplicate error sudo apt-get update .Help me!

I trying update security ... sudo apt-get update And faiel... Reading package lists ... Done W: Duplicate sources.list http://archive.canonical.com/ubuntu/ precise entry / i386 partner Packages ...