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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Some files under `/` are owned by UID `501`, is this dangerous?

I just noticed that that the directory /usr was owned by UID 501 on my system. Such a user does not exist on my system, as verified by looking at /etc/passwd. Have I suffered a security breach, or is ...
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1answer
40 views

rkhunter warnings scan, what to do

When i run a scan with rkhunter i get 2 warnings, i checked the log file and warnings are as the following : first warning : Warning: The command '/usr/bin/unhide.rb' has been replaced by a script: ...
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1answer
42 views

How kernel allows a process to receive network data that do not belong to it? [closed]

Each process is assigned with port number when using network resource. A process can only send and receive network data from its assigned port number. How kernel allows security programs like IDS, ...
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1answer
157 views

Does an in-kernel firewall sit between the network access layer and Internet layer?

This question is a follow-up to my previous question. Logic for me to says that an in-kernel firewall sits between the network access layer and the Internet layer, because it needs to have access to ...
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2answers
398 views

What are ways to encrypt a password inside an environment variable

I have this file I use to set my username and password before exporting the value. #!/bin/bash echo -n "User:"; read user echo -n "Password:"; read -s password export ...
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2answers
63 views

Shredding an external HDD

How do I shred the data on an external HDD? I am trying shred "/media/me/New Volume/" but I get failed to open for writing: Is a directory. Why?
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1answer
86 views

How security programs like firewall, IPS and IDS have access to network data?

It is said that kernel responsible for the transport, internet and network access layers for a network data. Then, the network data is passed on the appropriate process based on port number. How ...
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1answer
53 views

Is it possible to remove the delay on wrong password? [duplicate]

So I type my password incorrectly from time to time. Sometimes for sudo sometimes for logging in to my (Ubuntu) machine. In either case, there is a two or three second delay before it gives me a ...
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2answers
268 views

gvfs-mount auto password

I would like to make shortcuts for gvfs mounts (I prefer to mount from the shell). For this, it is quite necessary/convenient not to have to enter the password for the ftp:// and sftp:// connections . ...
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2answers
111 views

which unix or linux command is used to change root password of remote machine(Just an IP address) without using SSH Login [closed]

which unix or linux command is used to change root password of remote machine(Just an IP address)? Suppose I just have an IP address of the target machine which is on my network, But I do not know ...
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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 ...
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2answers
135 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 ...
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2answers
51 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
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2answers
87 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 ...
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1answer
88 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." ...
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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 ...
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1answer
81 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 ...
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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?
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3answers
290 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
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1answer
61 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 ...
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2answers
43 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 ...
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2answers
134 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? ...
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2answers
90 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: ...
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1answer
272 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 ...
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0answers
79 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 ...
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2answers
70 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 ...
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1answer
70 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 ...
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6answers
574 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 ...
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3answers
181 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 ...
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0answers
62 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 ...
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1answer
101 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 ...
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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 ...
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1answer
73 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 ...
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2answers
250 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
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1answer
96 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
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2answers
105 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
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1answer
162 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 ...
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2answers
595 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
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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
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1answer
41 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
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1answer
496 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 ...
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2answers
49 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
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1answer
66 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 ...
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2answers
64 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
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1answer
91 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
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1answer
178 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 ...
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2answers
127 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 ...
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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 ...
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1answer
43 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 ...
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1answer
1k 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 ...