Questions tagged [unix]

Unix is a family of multiuser, multitasking operating system that is widely used in workstations, servers and embedded devices. The best-known Unix variant is Linux.

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174
votes
7answers
11k views

How can I protect myself from this kind of clipboard abuse?

Clipboard abuse from websites Many websites use JavaScript or CSS to stealthily insert or replace text in the user's clipboard whenever they copy information from the page. As far as I know this is ...
27
votes
5answers
8k views

Why should one use sudo? [duplicate]

Most modern Linux articles advice using sudo rather than logging into root. This advice is so ingrained, some distros don't automatically allow root login. Indeed they come pre-configured with sudo ...
7
votes
7answers
2k views

Is it wrong to root login with SSH?

I've long been under the impression that with unix, you should never login as root. Now I've started using Virtual Private Servers over at DigitalOcean, and some advice is to use SSH keys to login as ...
98
votes
7answers
37k views

How does hacking work?

I am specifically talking about web servers, running Unix. I have always been curious of how hackers get the entry point. I mean I don't see how a hacker can hack into the webpage when the only entry ...
18
votes
3answers
30k views

How do I ensure data encryption on Samba transmission on *NIX systems?

I have a heterogeneous system (both MS and *nix) that communicates with CIFS/SMB. How can I ensure proper data encryption at the application layer?
2
votes
4answers
28k views

Netcat IP Spoofing

I am connecting to a server nc -v 192.168.0.1 1111 But I want to do IP spoofing because the server on 192.168.0.1 only accepting commands from 7.7.7.7. We are two friends, I am 192.168.1.1, and my ...
59
votes
6answers
26k views

Unix execute permission can be easily bypassed. Is it superfluous, or what's the intention behind it?

The unix read permission is actually the same as the execute permission, so if e.g. one process has write access it's also able to execute the same file. This can be done pretty easily:First this ...
36
votes
3answers
4k views

Is passing sensitive data through the process environment secure?

Recently I have been looking for the possibility to pass sensitive information from one process to another (at process startup time) without passing it through the command line or without using a ...
52
votes
7answers
11k views

Why does one need a strong password on Unix?

SSH Server: I only allow public key authentication. Malicious Software: If it's running as my user it has access to my data and an internet connection, it's bad enough already. Yes, su access would ...
21
votes
5answers
4k views

Is it possible for a file that is non-executable and read-only to run malicious code?

On a POSIX system, is there a possibility for a file which is non-executable and read-only (aka with a mode 444) to run malicious code on a machine? If so, can you explain how it would do so?
-5
votes
3answers
5k views

Why are people saying that the X Window System is not secure?

Why are people saying that the X Window System is not secure? The OpenBSD team succeeded with privilege separation in 2003; why didn't the "Linux developers" do this? To be clear: What security ...
11
votes
2answers
2k views

How is the available entropy in /dev/random calculated (or estimated)?

It seems (to a non-expert) that /dev/random is acclaimed to be useable as a source of pure random data. However, I am curious as to the analysis of the file /dev/random. /dev/random is a collection ...
7
votes
1answer
598 views

How can utilities with setuid set to root be secure if they are debuggable?

Today I heard at Uni something that broke my mental model about separation of users' rights. Namely, I heard that: I can freely debug all programs I have the permission to run, even those that have ...
9
votes
1answer
2k views

Is symlink race a very common vulnerability in UNIX systems

As far as I know, when I am creating a new file or directory in a directory that can be written by multiple users (and thus an adversary can have made a symlink there), the only way to protect myself ...
8
votes
1answer
754 views

Unix command to generate cryptographically secure random string

Is the following Unix command cryptographically secure to randomly generate 20 characters (a-zA-Z0-9 only)? dd if=/dev/urandom bs=256 count=1 2> /dev/null | LC_ALL=C tr -dc 'A-Za-z0-9' | head -c20 ...
3
votes
2answers
591 views

How to track down and remove Mac malware that is calling out? [duplicate]

Little Snitch periodically brings up a dialog that says: Terminal via node wants to accept an incoming connection from X on port 3000 (remoteware-cl). X are different IPs in eastern europe. A full ...
3
votes
2answers
2k views

How to remove meta and sensitive data from PDF file?

I've some PDF files generated from different sources (such as web-browser, Photoshop, etc.) on Unix. How do I make sure PDF doesn't contain any sensitive information such as IP address, OS, user name,...
3
votes
1answer
247 views

What is a good method to report security breaches that are being used to actively spam?

I received an email the other day purporting to be from a bank I hadn't even heard of, so I decided to poke around. On some quick investigation, it looks like something has just latched onto some poor ...
3
votes
3answers
110 views

Are environment variables entered *directly* before a command visible to other users?

UPDATE: I know that environment variables are generally secure, and am familiar with this question. My question is can other users see them if they are entered as part of a command (same line, no semi-...
2
votes
2answers
597 views

Why superuser or administrator account should never locked?

Why should administrator or superuser account never locked regardless how many incorrect login attempts are made? What should be done instead to alert the staff to the attempted instrusion?