All Questions

1176
votes
23answers
241k views

XKCD #936: Short complex password, or long dictionary passphrase?

How accurate is this XKCD comic from August 10, 2011? I've always been an advocate of long rather than complex passwords, but most security people (at least the ones that I've talked to) are against ...
1123
votes
3answers
605k views

How does SSL/TLS work?

How does SSL work? I just realised we don't actually have a definitive answer here, and it's something worth covering. I'd like to see details in terms of: A high level description of the protocol. ...
811
votes
12answers
225k views

How to securely hash passwords?

If I hash passwords before storing them in my database, is that sufficient to prevent them being recovered by anyone? I should point out that this relates only to retrieval directly from the database,...
782
votes
14answers
142k views

What technical reasons are there to have low maximum password lengths?

I have always wondered why so many websites have very firm restrictions on password length (exactly 8 characters, up to 8 characters, etc). These tend to be banks or other sites where I actually care ...
595
votes
5answers
240k views

Do any security experts recommend bcrypt for password storage?

On the surface bcrypt, an 11 year old security algorithm designed for hashing passwords by Niels Provos and David Mazieres, which is based on the initialization function used in the NIST approved ...
562
votes
23answers
134k views

How does changing your password every 90 days increase security?

Where I work I'm forced to change my password every 90 days. This security measure has been in place in many organizations for as long as I can remember. Is there a specific security vulnerability ...
538
votes
20answers
77k views

How can I explain SQL injection without technical jargon?

I need to explain SQL injection to someone without technical training or experience. Can you suggest any approaches that have worked well?
532
votes
3answers
486k views

What's the difference between SSL, TLS, and HTTPS?

I get confused with the terms in this area. What is SSL, TLS, and HTTPS? What are the differences between them?
518
votes
18answers
109k views

Police forcing me to install Jingwang spyware app, how to minimize impact?

Chinese police are forcing whole cities to install an Android spyware app Jingwang Weishi. They are stopping people in the street and detaining those who refuse to install it. Knowing that I may be ...
500
votes
11answers
74k views

Is my developer's home-brew password security right or wrong, and why?

A developer, let's call him 'Dave', insists on using home-brew scripts for password security. See Dave's proposal below. His team spent months adopting an industry standard protocol using Bcrypt. ...
495
votes
6answers
139k views

How to store salt?

If you expect to store user password securely, you need to do at least the following: $pwd=hash(hash($password) + salt) Then, you store $pwd in your system instead of the real password. I have seen ...
447
votes
8answers
424k views

RSA vs. DSA for SSH authentication keys

When generating SSH authentication keys on a Unix/Linux system with ssh-keygen, you're given the choice of creating a RSA or DSA key pair (using -t type). What is the difference between RSA and DSA ...
434
votes
13answers
90k views

Are passwords stored in memory safe?

I just realized that, in any language, when you save a password in a variable, it is stored as plain text in the memory. I think the OS does its job and forbids processes from accessing each other's ...
414
votes
13answers
98k views

Is it bad practice to use your real name online?

On some accounts I use my real name on-line (Google+/Facebook/Wikipedia/personal blog), others (Q&A/Gaming) I use an alias. My question is: Security and privacy wise, what can people do with my ...
383
votes
14answers
57k views

How is it possible that people observing an HTTPS connection being established wouldn't know how to decrypt it?

I've often heard it said that if you're logging in to a website - a bank, GMail, whatever - via HTTPS, that the information you transmit is safe from snooping by 3rd parties. I've always been a little ...
351
votes
22answers
300k views

I found that the company I work for is putting a backdoor into mobile phones

I have found out recently that the remote assistant software that we put in a smartphone we sell can be activated by us without user approval. We are not using this option, and it is probably there ...
299
votes
25answers
44k views

Should I let my child's school have access to my kid's personal laptop?

My kid is starting 6th grade and the school requires him to get a laptop and bring it to school. Now the school IT department wants to install some software on the laptop and is asking for ...
298
votes
9answers
168k views

Is BASIC-Auth secure if done over HTTPS?

I'm making a REST-API and it's straight forward to do BASIC auth login. Then let HTTPS secure the connection so the password is protected when the api is used. Can this be considered secure?
292
votes
7answers
41k views

Is it normal for auditors to require all company passwords?

My company is currently engaged in a security audit framed as a pentest. They've requested all admin passwords for every one of our services and all source code of our software. They want logins for ...
288
votes
16answers
57k views

SQL injection is 17 years old. Why is it still around?

I'm no techie and would like your expertise in understanding this. I recently read a detailed article on SQLi for a research paper. It strikes me as odd. Why do so many data breaches still happen ...
287
votes
20answers
48k views

How can someone go off-web, and anonymise themselves after a life online?

With data mining tools like Maltego and other correlation tools for large data sets, if we conduct any transactions online assume that these can all be collated to build a good picture of what we do, ...
286
votes
3answers
68k views

CRIME - How to beat the BEAST successor?

With the advent of CRIME, BEAST's successor, what possible protection is available for an individual and/or system owner in order to protect themselves and their users against this new attack on TLS?
281
votes
6answers
219k views

What is certificate pinning?

I'm superficially familiar with SSL and what certs do. Recently I saw some discussion on cert pinning but there wasn't a definition. A DDG search didn't turn up anything useful. What is certificate ...
280
votes
7answers
68k views

What's the rationale behind Ctrl-Alt-Del for login

Why is Ctrl+Alt+Del required at login on certain Windows systems (I have not seen it elsewhere, but contradict me if I'm wrong) before the password can be typed in? From a usability point of view, it'...
279
votes
9answers
67k views

Why is Gbt3fC79ZmMEFUFJ a weak password?

On https://passwordsgenerator.net/, it says Examples of weak passwords: qwert12345, Gbt3fC79ZmMEFUFJ, 1234567890, 987654321, nortonpassword The first, third, and fourth examples are obviously weak....
279
votes
6answers
122k views

How does Google know where I am?

Whenever I open the Google Maps app on my Android mobile phone, Google always seems to know my location, and it is very accurate (usually it places me on the map even in the correct room). Also, this ...
278
votes
3answers
21k views

How did “tech-supportcenter” phishers trick Google?

Related: Is the Web browser status bar always trustable? How can Google search change the location in a URL tooltip? I've always thought you can "hover" over a link to see where it really goes, ...
275
votes
9answers
39k views

What makes Docker more secure than VMs or bare metal?

I recently had a discussion with a Docker expert about the security of Docker vs. virtual machines. When I told that I've read from different sources that it's easier for code running within a Docker ...
253
votes
11answers
37k views

How to explain Heartbleed without technical terms?

Most of my friends who are not experienced in computers want to know what Heartbleed is and how it works. How would one explain Heartbleed to someone without a technical background?
253
votes
5answers
29k views

Consequences of the WPA2 KRACK attack

Today new research was published on vulnerabilities in wireless network security called Krack. What are the real-world consequences of these attacks for users and owners of wireless networks, what ...
251
votes
8answers
375k views

“Diffie-Hellman Key Exchange” in plain English

Can someone explain to me what Diffie-Hellman Key Exchange is in plain English? I have read in a non-tech news page that Twitter has just implemented this technology which allows two persons to ...
246
votes
8answers
930k views

How to find live hosts on my network?

I am trying to find the live hosts on my network using nmap. I am scanning the network in Ubuntu using the command sudo nmap -sP 192.168.2.1/24. However, I am unable to find the live hosts. I just get ...
246
votes
3answers
330k views

Why is 'Bearer' required before the token in 'Authorization' header in a HTTP request?

What exactly is the difference between following two headers: Authorization : Bearer cn389ncoiwuencr vs Authorization : cn389ncoiwuencr All the sources which I have gone through, sets ...
244
votes
11answers
58k views

Why shouldn't we roll our own?

Why shouldn't we create our own security schemes? I see a lot of questions around here about custom crypto and custom security mechanisms, especially around password hashing. With that in mind, I'm ...
244
votes
10answers
81k views

How is the “WannaCry” Malware spreading and how should users defend themselves from it?

There's a new strain of attacks which is affecting a lot of systems around the world (including the NHS in the UK and Telefonica in Spain) which is being called "WannaCry" amongst other names. It ...
243
votes
8answers
70k views

Why are salted hashes more secure for password storage?

I know there are many discussions on salted hashes, and I understand that the purpose is to make it impossible to build a rainbow table of all possible hashes (generally up to 7 characters). My ...
243
votes
5answers
19k views

Is the save button delay in a Firefox download dialog a security feature? What does it protect?

When I click to download a file through Firefox, a dialog window appears asking me whether I want to save the file somewhere or open it immediately once downloaded. The OK button in the dialog window ...
242
votes
4answers
109k views

SSL3 “POODLE” Vulnerability

Canonical question regarding the recently disclosed padding oracle vulnerability in SSL v3. Other identical or significantly similar questions should be closed as a duplicate of this one. What is the ...
238
votes
7answers
41k views

How do certification authorities store their private root keys?

Knowledge of a CA private key would allow MitM attackers to transparently supplant any certificates signed by that private key. It would also allow cyber criminals to start forging their own trusted ...
237
votes
17answers
26k views

Passwords being sent in clear text due to users' mistake in typing it in the username field

Upon reviewing the Logs generated by different SIEMs (Splunk, HP Logger Trial and the AlienVault platform’s SIEM) I noticed that for some reason quite a few users tend to make the mistake of typing ...
235
votes
12answers
23k views

Is single quote filtering nonsense?

Penetration testers found out that we allow single quotes in submitted data fields, and want us to apply rules (input validation) to not allow them in any value. While I'm aware that single quotes ...
230
votes
14answers
40k views

My college is forcing me to install their SSL certificate. How to protect my privacy?

My college administration is forcing us to install Cyberoam Firewall SSL certificate so that they can view all the encrypted traffic to "improve our security". If I don't install the certificate than ...
229
votes
3answers
33k views

Why did I have to wave my hand in front of my ID card?

I recently had to authenticate myself online to use an internet-based service. The authentication process was done via video call with me holding my ID card in front of my laptop camera beside my face....
229
votes
7answers
36k views

All 0s (zeros) in a bank card's CVC code

My bank card recently expired. I got a new one and this one turned out to be "lucky": its CVC code was 000. For a few months I used it extensively, both online and offline, without any difficulties - ...
229
votes
5answers
141k views

What is the difference between https://google.com and https://encrypted.google.com?

Is it there any difference between the encrypted Google search (at https://encrypted.google.com) and the ordinary HTTPS Google search (at https://google.com)? In terms of security what were the ...
228
votes
7answers
45k views

Why would you not permit Q or Z in passwords?

Jetblue's password requirements specify that, among other stringent requirements: Cannot contain a Q or Z I can't fathom a logical reason for this, unless it were say, extremely common for the ...
228
votes
15answers
32k views

Tracing the location of a mobile IP from an email

I'm a TV scriptwriter - and not hugely tech-savvy, so please bear with me... If the police have an email, sent by a suspect over a 3G or 4G network, could they use the IP address (since they know ...
225
votes
10answers
74k views

Is “the oft-cited XKCD scheme […] no longer good advice”?

I was stumbling around and happened onto this essay by Bruce Schneier claiming that the XKCD password scheme was effectively dead. Modern password crackers combine different words from their ...
225
votes
11answers
108k views

Why are hash functions one way? If I know the algorithm, why can't I calculate the input from it?

Why can't a password hash be reverse engineered? I've looked into this ages ago and have read lots on it, but I can't find the explanation of why it can't be done. An example will make it easier to ...
221
votes
7answers
81k views

Password Hashing: add salt + pepper or is salt enough?

Please Note: I'm aware that the proper method for secure password storage hashing is either scrypt or bcrypt. This question isn't for implementation in actual software, it's for my own understanding. ...

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