Content related to computer security.

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9
votes
2answers
800 views

How does ps know to hide passwords?

Witness: $ ps f PID TTY STAT TIME COMMAND 31509 pts/3 Ss 0:01 -bash 27266 pts/3 S+ 0:00 \_ mysql -uroot -p 25210 pts/10 Ss+ 0:00 /bin/bash 24444 pts/4 Ss 0:00 ...
8
votes
3answers
99 views

Trap: can't su as root, can't change group to wheel, ssh as root prohibited

Is this a trap? I made these steps in FreeBSD 10: 1) ssh as root prohibited 2) logged as user 3) su as root 4) as root chsh changed name of user "user" to "luser" 5) exit from ...
14
votes
4answers
13k views

What is the point of sshd “UseDNS” option?

I know what it does, but i don't know why. What attack(s) does it prevent ? Is it relevant for all kind of authentication methods ? (hostbased, password, publickey, keyboard-interactive ...)
11
votes
4answers
6k views

How should one set up full-disk encryption on OpenBSD?

Is there a preferred method to set up full-disk encryption under OpenBSD, similar to dm-crypt under Linux? I'm looking for full-disk encryption, as if someone were to steal my notebook they could ...
4
votes
6answers
412 views

Any program like `sudo` to gain root by having two users enter a password?

I run a server which is used by a group of individuals for e-mail, mailing lists, personal web homes etc. I thought about ways to provide root access for other members to allow them handling problems ...
13
votes
6answers
2k views

Can root/superuser read my read-protected files?

On shared unix hosting, if I have a file sensitive-data.txt and I issue: chmod 600 sensitive-data.txt Can root user still read my file? Specifically I'm wondering if it's safe to store my password ...
1
vote
0answers
31 views

Ulimits and pam modules

Can you explain me the relation of ulimit setting on a proccess and line session required pam_limits.so in pam module. In wich modules i really require this line? I have this line in pam.d/su ...
1
vote
1answer
86 views

File monitoring to pre-empt hacker

We have a hacker occasionally attempting to hack a site, and so far unsuccessful, but I would like a way to determine if the site has been compromised (i.e., files edited). The type of attacks are LFI ...
3
votes
1answer
94 views

present users a login prompt? /bin/login? getty?

I have a service that execs a command when a user connects to it through a socket, and redirects everything it receives to the executed program. It works ok with shells like bash, giving the user a ...
2
votes
1answer
52 views

Using LDAP for authentication, how can I safely disable/deactivate an account without deleting it?

We use LDAP for authentication for thousands of users. The primary tactic we have been employing to make a user unable to login, without removing their account, is to change the LDAP attribute ...
-2
votes
1answer
51 views

How to compile c, c++ and python code as “Released/Final” version? [closed]

I want to know if there are ways to compile C, C++ and Python code in order to not be able to reverse engineering it over Linux or not? I have heard there are some ways over Windows to do it, but I ...
5
votes
2answers
168 views

Writing a “telnet server” type program that uses SSH instead of telnet

So people have written server programs using telnet in which the user simply does telnet server.com and this connects them to the server program, which then provides them with a textual program they ...
3
votes
1answer
44 views

How does iptables recognize packet state?

Consider these two sets of rules: Set A -A INPUT -m conntrack --ctstate ESTABLISHED,RELATED -j ACCEPT -A INPUT -j REJECT -A OUTPUT -j ACCEPT Set B -A INPUT -m conntrack --ctstate ...
3
votes
2answers
44 views

using SUID bit to drop privileges

So this is a description of the system I'm working on : a "manager" process spawns all the other applications. The manager application runs as root user. so now, any process that it spawns also ...
2
votes
2answers
705 views

rkhunter warn me about root.rules

I run : :~$ sudo rkhunter --checkall --report-warnings-only One of the warnings I've got : Warning: Suspicious file types found in /dev: /dev/.udev/rules.d/root.rules: ASCII text and ...
8
votes
3answers
4k views

How to “close” open ports?

A few days ago I started to care a lot about my data security, I end up nmaping myself with: nmap 127.0.0.1 Surprise, surprise, I have lots of active services listen to localhost: $ nmap 127.0.0.1 ...
2
votes
2answers
173 views

Do I need to encapsulate awk variables in quotes in order to sanitize them?

As per an answer on stackoverflow, it's my understanding that encapsulating bash variables in double-quotes is a fairly safe way of sanitizing user input. What about awk variables? For example, if ...
0
votes
1answer
80 views

Is it possible to make a standard user that can gain NO access to root?

I'm a very new beginner learning how to use Linux. I have very little experience so far in different distros. I've set Kali Linux as the OS on a remote PC. Users will be connecting to it via SSH and I ...
2
votes
1answer
53 views

How it is decided which certificate of a Certificate Authority will be used in a system certificate chain [closed]

I am looking for PKI (Public Key Infrastructure) knowledge and particularly at OS's built-in certificate chain list. Of course on Windows the company decides which certificate will be built-in, but ...
0
votes
1answer
34 views

Maximum password length

Is there a maximum password length on unix systems? If so, what is that limit and is it distribution dependent?
4
votes
1answer
150 views

Why Nmap fragmented scan on Linux is only working from virtual environment?

OLD QUESTION AND TITLE (Look further down for the updated question): Why Nmap fragmented scan is only working on Backtrack? I spent quite a few hours today trying to capture and study some ...
7
votes
4answers
920 views

How to set up two-factor authentication with OTP on FreeBSD?

I have a FreeBSD hosted server that I like to be able to get to from anywhere. Normally I use SSH publickey to log in, or if I don't have my SSH private key available then I might use regular password ...
0
votes
2answers
37 views

Will autologin create remote security problems?

In Debian, I setup nodm, such that my computer logs in automatically when it is turned on. I am not concerned about thieves accessing the computer directly, but compared to a setup using GDM, can such ...
0
votes
1answer
1k views

fopen: $JOHN/dynamic.conf: No such file or directory

I have an unshadowed db.txt file: [root@SERVER ~]# rpm -qa | grep -i john john-1.7.9-1.el6.rf.x86_64 [root@SERVER ~]# head -1 /etc/issue Scientific Linux release 6.3 (Carbon) [root@SERVER ~]# cat ...
4
votes
1answer
47 views

What is not accessible from userspace?

I read somewhere (3.1.3) that there's a high ring (supervisor mode) and a low ring (user mode) and that some "things" can be run only from the highest ring. What do they mean by "things"? I'd guess ...
1
vote
1answer
52 views

How can I protect my computer when the only way to access the internet is though a compromised internet connection?

I access the network through a connection which is most likely compromised by a MITM attack. I can't do much about it. What steps should I take to lessen the influence of this attack. I'm especially ...
-1
votes
2answers
51 views

Is my system compromised or vulnerable to attacks

I ran netstat -lntup with the network connected. Recently one of my friends exploited my linux system using backtrack so I had to format it. Now I want to know whether I'm still being exploited or ...
3
votes
1answer
82 views

Has my machine been compromised?

I have a bunch of lines in my machine if I use "ps aux". Here are the lines: samp 8413 0.0 0.0 968 564 ? S 12:28 0:00 ./ssh 150 samp 8419 0.0 0.0 956 380 ? ...
3
votes
1answer
81 views

How do I change the Java Security level?

We've got an ancient (internal use only) self-signed app that refuses to run now with the changes to the JRE. Working on getting a code signing certificate and rebuilding it, but that's horribly slow ...
6
votes
1answer
263 views

Any random password results in successful login on tty

I can login to my machine (FreeBSD 9.1-RELEASE) for any user (for example: root or operator or any that exists in /etc/passwd) with any random password that I type... I tried to reset password for ...
1
vote
2answers
66 views

What ports are essential and should generally be allowed on a Linux system?

I'm running a desktop computer, but one with high threat risk. I've blocked all ports using a firewall except: HTTP, HTTPS, DNS, one port for torrent client. Do any common processes in distros ...
0
votes
1answer
39 views

Is this method safe or recommended for moving a /home directory?

I have my linux install on a small disk. I want to put the home directory on a different hard-drive. I was thinking of using this and then this. Would this work? Is there a better way? Should I just ...
3
votes
2answers
777 views

Sign a module after kernel compilation

I've built a kernel in tmpfs, then I rebooted. Now I see a message when I compile the 3rd party module, NO SIGN [M] XXXX.ko How can I get it signed? The key pair generated during rpmbuild is lost ...
1
vote
1answer
242 views

How to Block SSH Brute Force via Iptables and How does it work?

I'm planning to add the following rules to iptables to stop ssh brute force attack which are common these days. -A INPUT -i eth0.103 -p tcp -m tcp --dport 4522 -m state --state NEW -m recent --set ...
22
votes
2answers
1k views

Is it safe to give out my SSH public key for work?

I currently work remotely for a number of organizations which need me to access their servers regularly for maintenance and upgrades. Is it safe for me to add my RSA public SSH key to the ...
3
votes
1answer
75 views

How to disable root user on OpenBSD?

So there is a desktop and root permission isn't needed on it (or if it's needed, then reboot to single mode/whateverlivecd fix a config file-> get root, do the stuff with it and at the end, disable ...
2
votes
1answer
105 views

Nemo: Forget encryption password

I have mounted an encrypted disk by selecting it in Nemo (1.1.2), then typing a password. I can unmount the disk using Nemo, but now it can be remounted without requiring the password. Probably ...
2
votes
2answers
88 views

Why does sshd requires an absolute path?

Why does sshd require an absolute path when restarting, e.g /usr/sbin/sshd rather than sshd Are there any security implications? P.S the error message: # sshd sshd re-exec requires execution with ...
2
votes
1answer
49 views

Reconfigure login through root ftp (lost ssh access)

My question is twofold. I need to somehow re-enable telnet and/or ssh in a device where I currently only have root ftp access. Also, if I am going about this wrong, please let me know. Details to ...
4
votes
2answers
262 views

Purpose of using setuid() in SUID programs

I wonder that an SUID program like passwd is using the setuid() function call. Why does it drop root privileges? Against what types of attack does this help? Buffer-overflow?
2
votes
1answer
145 views

Was my Unix server compromised?

Someone asked if this constituted a break-in and wondered if their server had been compromised. Jan 12 04:16:51 foo sshd[26725]: Failed password for root from 61.174.51.207 port 1076 ssh2 Jan 12 ...
0
votes
1answer
64 views

Break In Attempt

mysql service has vanished from my vps and service is down since yesterday where can see from /var/log/secure file it says break in attempt from an ip that is not known to me but cannot tell if the ...
4
votes
2answers
68 views

What are the methods to protect home folder files from other applications runing as the same user?

I would like to enforce the security access of some files in my Home folder. My concern is about processes running with the same privileges as me having access to those files. I've been wondering ...
3
votes
1answer
47 views

Run Windows program on Linux in a secure way

I am trying to find a way to achieve a secure execution of Windows programs inside a Linux installation. I suppose that a Windows malware should not do any damage (infect the machine), if executed ...
2
votes
4answers
75 views

Keeping my production webserver updated

I have a production webserver (CentOS 6.5) and I just wanted to know how do I keep this updated interms of security updates and stable. For example, is it safe interms of not breaking anything on the ...
3
votes
2answers
959 views

Protecting postfix from bruteforce attacks

a few days ago I've set up a VPS, including personal SMTP service using postfix + procmail under Debian / Wheezy. I am already seeing a LOT of hammering onto the SMTP and other ports. Here's an ...
35
votes
9answers
1k views

How to trigger a system self destruct with a certain password is entered

How do I configure my system to destroy all personal data when a certain password is entered? The motivation behind this being NSA stuff. I imagine there being three primary usage cases. At login, ...
1
vote
1answer
65 views

How to make my laptop safe & secure from any accidents like deleting by mistake?

This should be a general question. This Q sprung my mind yesterday late evening because I accidentally deleted files from another partition rather than from the partition I was intending to do. I'm ...
5
votes
1answer
93 views

Secure access to remote SSH tunnel

So I wish to be able to access my Raspberry Pi (which I keep at home behind a firewall) remotely. One option is to use a static IP address, but as a poor student I don't want to fork out for one, and ...
6
votes
8answers
9k views

Is it possible to test user name and password?

I've written a python CGI script that invoke bash commands, and it needs to test for a successful login on the host. Is it possible to create a bash script that will test a given username and ...