Questions tagged [security]

The protection of computer systems and information from threats such as theft or data destruction.

The tag is used in the context of computer security.

Computer Security is a very broad term:

The objective of computer security includes protection of information and property from theft, corruption, or natural disaster, while allowing the information and property to remain accessible and productive to its intended users.

Questions on Super User tagged are generally expected to relate to specific software or hardware problems associated with security considerations.

Questions about protecting information assets from threats through controls, security architecture and security management systems are generally better suited for Security.StackExchange.

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5369 questions
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How are pseudorandom and truly random numbers different and why does it matter?

I've never quite got this. Just say you write a small program in any language at all which rolls some dice (just using dice as an example). After 600,000 rolls, each number would have been rolled around 100,000 times, which is what I'd expect. Why…
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How to fix warning about ECDSA host key

I'm trying to setup password-less SSH on an Ubuntu server with ssh-copy-id myuser@myserver, but I'm getting the error: Warning: the ECDSA host key for 'myserver' differs from the key for the IP address '' What's causing this, and how…
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How do I list the SSL/TLS cipher suites a particular website offers?

How can I retrieve a list of the SSL/TLS cipher suites a particular website offers? I've tried openssl, but if you examine the output: $ echo -n | openssl s_client -connect CONNECTED(00000003) depth=1 /C=ZA/O=Thawte Consulting…
Jeremy Powell
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How can I give my wife emergency access to logins, passwords, etc.?

I'm the digital guru in my household. My wife is good with email and forum websites, but she trusts me with all our important digital stuff — online banking and other things that require passwords; also family photos and the plethora of other…
Torben Gundtofte-Bruun
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How to reliably keep an SSH tunnel open?

I use an SSH tunnel from work to go around various idotic firewalls (it's ok with my boss :)). The problem is, after a while the ssh connection usually hangs, and the tunnel is broken. If I could at least monitor the tunnel automatically, I could…
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How to mess up a PC running Windows 7?

Ok, so for my PC class I have to find 3 hacks that would mess up the lab's PC. Me and my partner are going to mess up the PC and then another team will try to fix it. The system on it is Windows 7. Anything that would stop the normal use or render…
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"This file came from another computer..." - how can I unblock all the files in a folder without having to unblock them individually?

Windows XP SP2 and Windows Vista have this deal where zone information is preserved in downloaded files to NTFS partitions, such that it blocks certain files in certain applications until you "unblock" the files. So for example if you download a zip…
Tom Kidd
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How do I view the contents of a PFX file on Windows?

I have a PFX certificate file on my machine and I'd like to view the details before importing it. (The import utility doesn't actually tell you what the certificate is!). How do I view the details about the PFX certificate file?
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How to password protect gzip files on the command line?

I want to create some tar.gz (and possibly tar.bz2) files, using the tar command on Ubuntu 10.04. I want to password protect the file. What is the command to do this (I have Googled, but found nothing that shows how to create and extract compressed…
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How to wipe free disk space in Linux?

When a file is deleted, its contents may still be left in the filesystem, unless explicitly overwritten with something else. The wipe command can securely erase files, but does not seem to allow erasing free disk space not used by any files. What…
Alex B
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Is it really possible for most enthusiasts to crack people's Wi-Fi networks?

Can most enthusiastic users (even if they are not professionals) use well-known techniques to break through the average home router's security? Some basic security options are: strong network password with various encryption methods custom router…
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How does Linux know that the new password is similar to the previous one?

A few times I tried to change a user password on various Linux machines and when the new password was similar to the old one, the OS complained that they were too similar. I always wondered, how does the system know this? I thought that the password…
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Why does my browser think that is secure?

When I visit, any web browser I use considers the URL to be secure. This is what Google Chrome shows: Normally, when I try to visit an HTTPS site via its IP address, I get a security warning like this: From my understanding, the…
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What is the danger of inserting and browsing an untrusted USB drive?

Suppose someone wants me to copy some files to their USB stick. I'm running fully-patched Windows 7 x64 with AutoRun disabled (via Group Policy). I insert the USB drive, open it in Windows Explorer and copy some files to it. I do not run or view any…
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SSH: The authenticity of host can't be established

What does this message mean? Is this a potential problem? Is the channel not secure? Or is this simply a default message that is always displayed when connecting to a new server? I am used to seeing this message when using SSH in the past: I…
Steven Lu
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