Content related to computer security., i.e. content about policies, mechanisms, etc. needed make sure data is not leaked or corrupted and services available in all circumstances.

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9
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4answers
1k views

Sudoers for one day per week?

I have been volunteered by my boss to be the sysadmin for our production redhat server. He asked me to tighten the security to avoid mishaps like rm -f * that occured not long ago. Right now, we ...
3
votes
2answers
114 views

Process in user mode switch to kernel mode. Then the process will have root privileges?

According to http://www.linfo.org/kernel_mode.html in paragraph 7: When a user process runs a portion of the kernel code via a system call, the process temporarily becomes a kernel process and is ...
1
vote
2answers
46 views

if an exploit is affecting MS office does it affect also LibreOffice? [closed]

This question is really annoying me a lot and I want a reasonable, certain, logical... response for it
1
vote
2answers
76 views

Game server hosting and security

I'm working on a small controlpanel for a hobby project of mine, which is supposed to set up game servers. But I have some concerns regarding security that I would like some input on. My first idea ...
1
vote
1answer
84 views

Is this what it looks like in the terminal on the client side when you are blocked out via fail2ban?

I am a new server admin. I just setup fail2ban on an ubuntu 12.04 VPS. I used this tutorial. Then I tried to login to the system via ssh from a friend's machine. It is showing "operation timed out." ...
1
vote
0answers
36 views

How can I hide a command line from (e.g.) top & htop? [duplicate]

I know that both support specifying the username, which can be forced using an alias in root-owned ~/.bashrc, but one can temporarily disable the alias by prepending the command with \, so what are ...
1
vote
1answer
69 views

Security for a web server for multiple people?

I have an apache web server set up where multiple people have their websites hosted, mostly php based websites. The problem is, when these people upload their website files, it has read permissions ...
1
vote
1answer
31 views

Are there GPG-signed OpenBSD ISOs with which I can verify an installation disc?

Are there GPG-signed OpenBSD ISOs that I can download and later verify the downloaded file? Or at least a GPG-signed shasum?
4
votes
3answers
225 views

Hidden Files&Directories in user's home directory [closed]

I am in my user's home directory, I do: ls -a Then it shows me large number of hidden files and directories in my user's directory. Which of them I am allowed to remove? Which ones are necessary ...
3
votes
1answer
56 views

Did this tutorial block pings to my server?

I am a programmer teaching myself linux admin stuff. I followed this tutorial to setup a firewall on a VPS. As a part of that tutorial, I block all traffic except for web traffic and SSH traffic. I ...
0
votes
2answers
41 views

Check that fail2ban is running?

I just installed and configured fail2ban. I want to make sure it is working. I don't want to block myself from the server so I can't just login (poorly) a bunch of times. How do I see that fail2ban is ...
0
votes
2answers
117 views

What is the default action for incoming packets that don't match explicit iptables rules?

CentOS 5.x I'd like to understand what is specifically happening to incoming packets that don't explicitly match rules in my iptables chains. Is the default action to reject them? Or drop them? ...
0
votes
2answers
76 views

Trying to use TLS SMTP against Exim, getting Security Error back; what's wrong?

OS: FreeBSD9 64 Bit MTA: EXIM4 with TLS with Self Signed Certificate. I am using telnet myserver.com 25 EHLO dummy@dummy.com STARTTLS It says TLS go ahead And then I issue MSG FROM: ...
3
votes
1answer
223 views

How can I install Linux on a UEFI system with Secure boot?

My motherboard is a Gigabyte 990XA-UD3 (CPU 1), it's a UEFI -Dual boot, and when I try installing Linux Mint 16 Cinnamon or Ubuntu 13.10 it always bring this error (initramfs) Unable to find a medium ...
1
vote
0answers
76 views

What keys are generated during Debian 7.4 (Wheezy) installation?

We are concerned lest /dev/random (or /dev/urandom) be hit too early in the installation process for adequate entropy to be developed. In a basic Debian 7.4 installation (SSH Server and basic ...
2
votes
2answers
69 views

In OS X Darwin, why can I interfere with text input across user sessions using cat?

OS X Darwin: Disrupting Terminal Sessions Across User Identities How, in Brief: with cat < /dev/ttys_, in Terminal. My Question This OS X 10.9.2 Darwin behaviour seems odd to me, and I would ...
1
vote
1answer
61 views

Is there a selinux, httpd, or PHP configuration that prevents reading mounted drives?

I'm moving a virtualized centos web server over that has an all-to-small hard drive to a new machine and I hooked up a bigger drive for hosting videos and downloads and stuff. W When I try to run a ...
1
vote
6answers
439 views

Program a file to self-destruct at a given time

Does anyone know whether there is a command in linux that can set attributes to file so that the file can disappear after certain time. For example, if I set one attribute to file as "1/1/2015", so ...
8
votes
3answers
169 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 ...
1
vote
0answers
57 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
95 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 ...
14
votes
6answers
3k 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 ...
-2
votes
1answer
66 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
230 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
82 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
92 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 ...
0
votes
1answer
143 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
2answers
479 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 ...
2
votes
1answer
55 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
39 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
290 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 ...
0
votes
2answers
46 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 ...
4
votes
1answer
61 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
votes
2answers
61 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
90 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
148 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 ...
1
vote
2answers
113 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 ...
1
vote
1answer
59 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 ...
0
votes
1answer
41 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 ...
1
vote
1answer
846 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 ...
2
votes
1answer
107 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 ...
3
votes
1answer
133 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
2answers
935 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
155 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
74 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
96 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
57 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
146 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 ...
5
votes
1answer
143 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 ...
1
vote
1answer
73 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 ...