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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125
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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 ...
99
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7answers
32k 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 ...
48
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6answers
11k 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 ...
26
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3answers
2k 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 ...
23
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5answers
4k 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 ...
20
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1answer
3k views

Is mosh now recommended by the security experts? (2014)

Mosh has been around for a while now. Although it's claimed to be "a replacement for SSH" by its authors, mosh does actually depend on ssh to do the initial authentication, after which an instance of ...
19
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5answers
3k 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?
15
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1answer
945 views

Linux /etc/shadow password change security

I wonder what happens what happens when I am changing my password on a Linux system. Basically all passwords are stored in a file called /etc/shadow or /etc/master.passwd in BSD-like systems as I do ...
14
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3answers
18k 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?
12
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7answers
576 views

UNIX Servers: Possible intrusions or attacks that do not use any of the open listen sockets

What type of attacks are there that do not use open TCP or open UDP ports? Is it safe to assume that no open ports means no remote access? (Excluding the possibility that there is a badware already ...
12
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4answers
7k views

OpenBSD vs. NetBSD security

If I search for the two words: OpenBSD and NetBSD on http://www.exploit-db.com/ then I get 17 hits regarding security bugs on OpenBSD, and 8 hits regarding security bugs on NetBSD. So what are the ...
11
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3answers
490 views

Is it insecure to have an SSH server on a workstation?

I know one systems administrator who runs SSH Server on his workstation to push files to it and check things from a phone but I think it is a bad idea for several reasons: An operations workstation ...
10
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4answers
909 views

Does UNIX have a dual approval mechanism?

Sudo and logging is used to keep administrators accountable. But is there a command/configuration that lets you enforce a dual approval type control such as the the "Two Person Concept"? (eg. Two ...
10
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3answers
6k views

Shellshock Bash bug on mobile systems

Does the bug in Bash affect Android or iOS mobile systems?
9
votes
2answers
1k 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 ...
8
votes
3answers
953 views

What prevents this exploit from working (unix SUID)?

If I have a user on a unix system where Im allowed to create new files, what prevents me from downloading an executable file onto that system which is already SUID'ed to root on a different system? ...
8
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4answers
5k views

SHA-512 unix passwords. How secure are those hashes, really?

I came across this very alarming sounding thread which indicates a GPU with about half the compute capacity of the GPU currently powering the monitor I type this on is capable of 11.5k c/s. I'm not ...
8
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2answers
276 views

Security of o=rwx with classical Unix permissions

Is it in anyway insecure to go o=rw or o=rwx on files and directories confined to directories that are marked o=? In other words, given private (g=,o=) home directory, is it perfectly safe to write ...
8
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2answers
3k views

What are the dangers of storing webserver temp files in the /tmp/ folder?

I have configured my first publicly accessible nginx server. I have configured it to use a /tmp/nginx folder to store temp files. This includes the body of http requests, proxy files etc. The /tmp ...
8
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1answer
261 views

What is your default umask set to?

What is your default umask set to? Did you run into any problem setting a stricter default umask?
7
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3answers
2k views

MSFConsole/Kali Linux - gain root access to unix system

I am messing around with Kali Linux, MSFConsole and DVWA (Damn Vulnerable Web Application). I have successfully been able to get into the system (Raspberry Pi) by creating a PHP backdoor and uploaded ...
7
votes
2answers
273 views

What output can a program, when executed from a command line, output to generate behavior that is a vulnerability on the terminal emulator?

Reading this post, titled "Fixing Unix/Linux/POSIX filenames", I came across a VERY interesting phrase by the author, which says: Oh, and don’t display filenames. Filenames could contain control ...
6
votes
3answers
221 views

Is it safe to attach a potentially malicious hard drive to a Solaris machine?

We bring in hard drives from un-trusted sources and would like to ensure that they will not contain any harmful content. What kind of risk is there for Solaris? As in, if Solaris is running, and I ...
6
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2answers
357 views

Where can I “hide” easter eggs for students learning about Linux security?

I feel like this isn't the best place to ask this (since there's no single right answer), but I can't think of a better place. If you have a better recommendation, could you please recommend it and I ...
6
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2answers
570 views

How a malware executes remote payload

Let's assume a malware was installed (on a UNIX-based platform) with some social engineering tricks. The original installed code itself may be benign, but the only malicious activity is that the ...
6
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2answers
267 views

How is the password prompt going to protect me from ruining my computer?

On Unix based systems, I'm often prompted to enter my password before installing or running a program. Why does this protect me? If I'm running a kiosk, I understand that a password might prevent ...
6
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1answer
494 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 ...
5
votes
3answers
256 views

Could browsers improve security of stored passwords by using setuid?

On Unix-esque systems, Mozilla Firefox stores a users' preferences, web history and stored passwords in a set of files that are readible and writeable by that particular user. This makes sense: when ...
5
votes
2answers
1k views

Can you describe a real-life scenario of exploiting sticky bits?

Sticky bit are mentioned in every UNIX security book, but I couldn't find anyone that describes the exploitation of Sticky Bit set on a file. Can you?
5
votes
3answers
2k views

Making passwd/shadow files more secure

The passwd/shadow files in a unix-like OS contain sensitive info such as a user's password. In addition those files aren't necessarily secured: with a live CD we can access those files on the hard ...
5
votes
3answers
13k views

Finding environment variables with gdb, to exploit a buffer overflow

I have to exploit a very simple buffer overflow in a vulnerable C++ program for an assignment and I am not being able to find the environment variable SHELL. I have never worked with BoF before, and ...
5
votes
2answers
747 views

Can UNIX Domain Sockets be locked by user ID?

If I created a folder /tmp/me with permissions 700, and started a process under me that starts a listen socket under /tmp/me/socket. I currently assume that a connection to that socket originated ...
5
votes
1answer
158 views

Why require root to be the first entry in /etc/passwd?

Security policies sometimes demand that root be the first entry in the /etc/passwd file. Is there a valid reason for requiring this, or is it just conventional to do so since the root account is the ...
5
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2answers
209 views

What is the meaning of the term “simple string” for the SALT string in Unix crypt using SHA-256 and SHA-512?

In Unix crypt using SHA-256 and SHA-512 the author, Ulrich Drepper, introduces the SALT string as the following (highlight by me): For the SHA-based methods the SALT string can be a simple string ...
4
votes
7answers
723 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 ...
4
votes
2answers
23k views

Where is my password stored on Linux? [duplicate]

Is there a specific location where the passwords are stored ? Is it depending on which version is used ? Are they salted ?
4
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2answers
62 views

Is it safe to expose a logging socket endpoint in a chrooted environment?

I'm trying to set up a file transfer server, which needs to be secured and logged. FTP was suggested, but that feels outdated so I automatically translated that to SFTP (OpenSSH) in my head. Using ...
4
votes
4answers
913 views

What mechanism enforces user permissions in Unix/Linux?

One of the core pieces of security in Unix/Linux systems is limiting privileges by user. For instance, certain actions can only be done by the root user. In theory, this can keep a malicious process ...
4
votes
1answer
8k views

what does it mean to be setuid root?

I am reading Tanenbaum's Modern Operating Systems 3e. He says "Suppose that the program being attacked [with malicious code] is SETUID root in UNIX (or has Administrator power in Windows). The [...
4
votes
2answers
125 views

What are the benefits of having multiple overwriting patterns for secure deletion? [duplicate]

When installing a new AIX server, there is a possibility to use several patterns for secure deletion. My question: Is it necessary to use several patterns? What is the benefit from having several ...
4
votes
1answer
142 views

Dangerous to open a unix socket within www root?

My web server is chrooted into /var/www, and its contents are available over the network. One of my web applications needs access to a unix socket, and so that socket needs to be somewhere in /var/...
4
votes
1answer
431 views

OpenBSD-based LiveCD/LiveDVD - is it secure? is it offical?

Does the OpenBSD LiveCD/LiveDVD get deeply audited like the original OpenBSD? Is it an official "port"? Experiences with it?
3
votes
2answers
813 views

vulnerable getlogin

I was reading "A taxonomy of Coding Errors" and I have a doubt regarding the point mentioned in C/C++ >> API Abuse >> Often Misused: Authentication(getlogin). I fail to understand the attack vector ...
3
votes
2answers
324 views

OBSD X11 as non-root?

If running X11 as root is not a very good idea, then can anyone mention a method/solution, how to still use a GUI, and not having X11 as root?
3
votes
1answer
59 views

Unauthorized file writes on Linux

Suppose my web browser or any other web-connected app has a minor security hole that won't allow an attacker to run code but will allow them to write a piece of text into a text file I own. On a ...
3
votes
1answer
199 views

S/Key as an alternative to UNIX passwords

There is this password system called S/Key I saw on the Internet. Can someone give me a brief description about S/Key and how it works? Can S/Key be an alternative solution to the UNIX password system?...
3
votes
5answers
2k views

Security purpose of asking admin password to mount partition on Linux

So I divided my 250GB laptop drive into 2 partitions and some swap. On the second partition which is an ext4 60GB partition I installed Fedora 17. On the other bigger NTFS partition I've got Win XP ...
3
votes
1answer
208 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
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2answers
198 views

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

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
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4answers
709 views

What RHSA, RHEA and RHBA stands for in the RedHat Erratas?

Do you know what does RHSA, RHEA and RHBA stands for in RedHat Errata ?