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

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595
votes
18answers
69k views

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 ...
339
votes
12answers
17k views

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 ...
283
votes
27answers
87k views

How to mess up a PC running Windows 7? [closed]

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. ...
151
votes
9answers
23k views

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 ...
149
votes
19answers
171k views

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 www.google.com:443 ...
148
votes
15answers
163k views

“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 ...
128
votes
5answers
12k views

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 ...
123
votes
13answers
78k views

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 ...
122
votes
9answers
9k views

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 ...
121
votes
5answers
12k views

How to identify whether my Linux computer was hacked?

My home PC is usually on, but the monitor is off. This evening I came home from work and found what looks like a hack attempt: in my browser, my Gmail was open (that was me), but it was in compose ...
117
votes
7answers
17k views

How to use the Internet while Heartbleed is being fixed?

There are many websites who are not currently vulnerable, but I have no idea if they were vulnerable a few days ago. For example: twitter.com: Not vulnerable right now, but the certificate is from ...
100
votes
15answers
166k views

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 ...
98
votes
23answers
14k views

How can I make a Windows PC bullet-proof for home users? [closed]

I realize that virus-proof on a Windows PC is far fetched, but in the interest of keeping time spent as the "family-tech-support" to a minimum, I am looking for ideas to lock a computer down to the ...
89
votes
10answers
7k views

Securely erasing all data from a hard drive

I am about to sell my old desktop PC and I am cautious about some of my sensitive information being available to the purchaser, even after reformatting the hard-drive, using data recovery software. ...
88
votes
3answers
50k views

“Google Software Update would like to control this computer…” What?

For the first time (that I've seen), some piece of Google's software updater is now asking for permission to control my computer. I couldn't find any other mention of this on the web, so I don't ...
86
votes
8answers
27k views

My colleague often shuts down my machine through the LAN - how do I prevent it?

This might sound weird. My colleague and I were working on a Windows machine. He frequently shuts it down through the LAN. He usually follows these steps: Access command prompt, enter shutdown -i. ...
78
votes
2answers
8k views

What makes Secure Login (CTRL+ALT+DEL) Secure?

I was reading about enabling CTRL+ALT+DEL as a security measure when logging in. My question is, what exactly is secure about it? What goes on "behind the scenes" that makes it safe from viruses and ...
76
votes
10answers
18k views

How to destroy a CD/DVD rom safely?

I have old CDs/DVDs which have some backups, these backups have some work and personal files. I always had problems when I needed to physically destroy them to make sure no one will reuse them. ...
73
votes
9answers
65k views

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 ...
70
votes
5answers
92k views

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 ...
70
votes
13answers
115k views

Which TrueCrypt Algorithm is the safest?

If performance is of no concern, which TrueCrypt algorithm is the safest to use? AES Serpent Triple DES Twofish AES-Twofish AES-Twofish-Serpent Serpent-AES Serpent-Twofish-AES Twofish-Serpent
69
votes
13answers
13k views

How is Linux not prone to viruses, malware and those kinds of things?

How is Linux protected against viruses? This question was a Super User Question of the Week. Read the blog entry for more details or contribute to the blog yourself
62
votes
8answers
94k views

How can I tunnel all of my network traffic through SSH?

Whenever I'm using the internet from an insecure location (such as public wifi) I like to use an ssh tunnel (ssh -D port host) to ensure my traffic can't be sniffed. Unfortunately, there seem to be ...
62
votes
3answers
143k views

What is 1e100.net and why do I have TCP ports open to it?

I see my PC has TCP connections open to 1e100.net. Then I checked the whois record and find it is registered to Google. Weird. A quick search seems to indicate that 1e100.net is pretty popular - ...
59
votes
6answers
4k views

Is there a point in installing antivirus on Ubuntu?

I have recently started using Ubuntu. I am wondering about the point of installing antivirus programs on Ubuntu. On SuperUser, I found the opinion that it only detects "windows viruses" and removes ...
56
votes
2answers
11k views

The MD5 hash value is different from Bash and PHP [duplicate]

I tried to generate the MD5 sum (using md5sum) of a string, "hello". I tried out different methods as the md5sum tool in Linux, PHP's MD5() function as well as various online text to md5sum ...
53
votes
5answers
3k views

How do anti-viruses work?

So I was thinking about viruses recently, and wondering how exactly antiviruses keep up? Considering anybody who'd been coding for a few weeks could hack together something do do nasty, nasty things ...
51
votes
5answers
4k views

What are the potential security issues when I keep using Windows XP? [closed]

Microsoft stopped updating Windows XP and the media warns us of security leaks. I actually just read that continuing to use Windows XP is "extremely" dangerous. Why exactly is this such a danger? I ...
51
votes
6answers
30k views

What is better for GPG keys - RSA or DSA?

ssh-keygen defaults to creating RSA keys, but gpg --gen-key prefers DSA/ElGamal. Which one - RSA or DSA - is better for GPG?
50
votes
2answers
6k views

What do you do if you are being hacked by something coming from a supposedly legitimate IP address such as from Google?

Earlier today I was prompted to use a CAPTCHA—because of suspicious search activity—when doing a Google search, So I assumed either a PC on my network had a virus or something. After poking around I ...
45
votes
4answers
3k views

Should I install Internet Explorer updates although I disabled it?

I have disabled Internet Explorer in the "Windows Features" dialog. Nonetheless Windows Update alerts me that there are security updates for IE. I am aware that I cannot uninstall IE and it remains ...
45
votes
1answer
10k views

Why does Google call Thunderbird “less secure”?

I've never had problems using Gmail with Thunderbird yet, but while trying to use a free software client for Google Talk/Chat/Hangout I've discovered that, according to Google's document on "less ...
43
votes
1answer
3k views

Short, easy to understand explanation of GPG/PGP for nontechnical people?

Does anyone have a link to a good, but short (1-2 paragraphs) explanation of the benefits of using GPG/PGP signing and encryption for Email focused at non-technical readers? That is, why would someone ...
42
votes
19answers
18k views

Destroy a hard drive without proper equipment

I need to make two hard drives unreadable. Unfortunately, I have some constraints which make this harder than usual (in particular, they rule out the answers to other questions): I don’t have a ...
42
votes
1answer
115k views

Give write permissions to multiple users on a folder in Ubuntu

There is a folder that is owned by user tomcat6: drwxr-xr-x 2 tomcat6 tomcat6 69632 2011-05-06 03:43 document I want to allow another user (ruser) write permissions on document folder. The two ...
41
votes
14answers
7k views

Would Microsoft Security Essentials be adequate protection? [closed]

Is Microsoft Security Essentials (MSE) adequate protection for my computer? What is the experience with this product? I found out about a comparison of AV Suites. MSE did VERY well. One that I ...
41
votes
6answers
3k views

Security Concern with my Windows 7 Box at Work

This question may be weird and misworded but I'm not a Windows expert by any means so feel free to correct me. The group I'm in recently got new computers at work. They gave me a new computer and ...
41
votes
3answers
5k views

How secure is the Windows clipboard?

I've been using the Windows clipboard as a method of getting passwords from Lastpass into desktop applications. I've been wondering exactly how secure is this? Can't any program access the clipboard ...
41
votes
1answer
43k views

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 ...
41
votes
8answers
17k views

How safe is Firefox password manager?

I have been using the Firefox password manager for long time, but never checked/verified how secure it is.
40
votes
2answers
7k views

Why do some websites show the company name next to the URL?

Some websites show the company name next to the URL (in Chrome) and some don't. How do I set this up for my website? Is there a reason why or why I wouldn't want to do this?
40
votes
6answers
48k views

scp to remote server with sudo

I have a file on server A (which is behind a NAT so not directly addressable). The file needs to be copied to server B in a directory restricted to root. I have an account on server B with sudo ...
39
votes
4answers
22k views

Which of the Windows updates are really necessary?

I downloaded a lot of Windows updates in the automatic mode. Are they all necessary? Can I remove some of them? How do we know which ones are necessary?
39
votes
8answers
31k views

How can I get a virus by just visiting a website? [duplicate]

Possible Duplicate: Can a computer be infected by malware through web browser? It is common knowledge that you can get a virus just by visiting a website. But how is this possible? Do ...
38
votes
1answer
11k views

How do I extract fingerprints from .ssh/known_hosts?

My laptop has a well-populated ~/.ssh/known_hosts file. I'd like to leverage that when connecting to remote hosts from my desktop, since tracking down the fingerprints can be a real chore. However, I ...
37
votes
12answers
7k views

What is the value of MD5 checksums if the MD5 hash itself could potentially also have been manipulated?

Downloads on websites sometimes have an MD5 checksum, allowing people to confirm the integrity of the file. I have heard this is to allow not only corrupted files to be instantly identified before ...
37
votes
3answers
77k views

How to run a cron job as a specific user?

I would like to run a cron job as a specific user on my machine. How may I specify the user for a cron job to run as?. I am running on Ubuntu 10.0.4 [Edit] The cron jobs will be running on a ...
37
votes
4answers
1k views

If a password is compromised, is a “similar” password also compromised?

Suppose a user uses a secure password at site A and a different but similar secure password at site B. Maybe something like mySecure12#PasswordA on site A and mySecure12#PasswordB on site B (feel ...
36
votes
2answers
22k views

Best encryption and signing algorithm for GnuPG: RSA/RSA or DSA/Elgamal? [closed]

I have found this relatively old question about whether RSA or DSA is the preferred algorithm for signing and encrypting with GnuPG. When using gpg --gen-key, the two relevant choices are either "RSA ...
35
votes
1answer
3k views

How to find source process of unknown popup in Windows 7

A random popup appears in Windows 7 titled as Information with a progress bar and a clock. The window sometimes says Please wait a moment..., and the progress bar moves very slowly and disappears. ...