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.

learn more… | top users | synonyms

12
votes
3answers
27k views

How to ensure SSH port is only open to a specific IP address?

This is my /etc/sysconfig/iptables: It has two ports open 80 apache and 22 for ssh. # Firewall configuration written by system-config-firewall # Manual customization of this file is not recommended. ...
42
votes
4answers
7k views

Why is root login via SSH so bad that everyone advises to disable it?

Everybody on the Internet advises to disable root login via SSH as it is a bad practice and a security hole in the system, but nobody explains why it is so. What is so dangerous in enabling root ...
2
votes
1answer
71 views

How to Mark Traffic using IPtables?

I'm trying to mark traffic, How shall I write following code in terms of IPtables? /ip firewall mangle> add chain=prerouting src-address=10.1.1.1/32 action=mark-connection \ ...
2
votes
1answer
36 views

What is the difference between the FreeBSD flags, immutable and unlink?

What are the differences or similarities among the FreeBSD flags, simmutable/uimmutable and sunlink/uunlink? Reading man chflags, I see these flags: schg, schange, simmutable set the system ...
1
vote
4answers
14k views

Helo command rejected: need fully-qualified hostname Error

My mail server is in some blacklist cause of spams. I reconfugured postfix. Aften then My customers get this error they can't send emails. 404 4.5.2 <PLLAMNAZIFE>: Helo command rejected: need ...
1
vote
0answers
59 views

nmap doesn't detect opened port [closed]

I'm testing some vulnerabilities on a machine which has the port 22333 opened (it's used as the ssh port, and I can connect to it without any problem and I can get connected as well with the telnet ...
1
vote
2answers
76 views

iptables configuration - ssh connection only from a remote network

I'm trying to configure Iptables of a server in order to permit SSH incoming connections only from a certain network. by the way this is the rule chain : # Drop anything we aren't explicitly ...
15
votes
2answers
459 views

Security implications of running perl -ne '…' *

Apparently, running: perl -n -e 'some perl code' * Or find . ... -exec perl -n -e '...' {} + (same with -p instead of -n) Or perl -e 'some code using <>' * often found in one-liners ...
2
votes
1answer
79 views

Using mailx without storing a password

I'm trying to setup mailx to use my Gmail account. I've found a configuration that can send mail successfully but it requires me to store my email password in a configuration file in my home ...
2
votes
3answers
55 views

Does a Certificate Authority represent my company or a server?

I am setting up my second OpenVPN server with TLS and so I have a question about CA. Should I create a separate CA for each server or use the same? Why? Both servers will cater to the same network ...
5
votes
1answer
66 views

How to enable random PIDs on Linux?

I'm currently comparing random PID implementation on OpenBSD, FreeBSD and Linux from security perspective. As long as OpenBSD and FreeBSD are concerned, my work is done. However, while the answer ...
1
vote
2answers
37 views

OpenVPN : protect your clients key/cert/conf from being stolen?

I have configured an OpenVPN install. Mode: multiclients 1server. Clients are raspberries. I note how easy it is to steal a rasp, and look in HDD to get key+cert+conf. Copy it on your laptop, and ...
8
votes
3answers
1k views

Is it a good practice to run a daemon under a non-root user account?

I've developed an application that uses NTP to change the network time, to sync two of my computers. It runs as root, since only the latter is allowed to change the time and date on Linux(I guess). ...
0
votes
0answers
17 views

Where to put the ASCII WPA2 Wifi Key in MacOS X?

I tried to make some research about wifi security in our company: So i tried to het WPA2 Wifi key using wifite tool in Kali linux distribution. After the few attempts i get WPS PIN and WPA2 KEY: ...
0
votes
1answer
45 views

What are the best practices for permissions and and methods for generally avoiding using sudo? [closed]

The main point is that I only want one user to have sudo access - really only for use in set up and emergencies. I don't even trust myself with sudo access all the time. Are there best practices ...
12
votes
6answers
56k views

How can I monitor all outgoing requests/connections from my machine?

My machine is a server so I want to ignore connections being made to my server (e.g. when someone visits my website). I want to see only connections/requests being made by my server to other places. ...
1
vote
0answers
47 views

What is the best operating system for beeing anonymous [closed]

Im looking for an anonymous distribution of linux, anyone can help me? Thanks
0
votes
4answers
88 views

How to track/log commands executed on a shell?

Can commands be written to a logfile before they were executed in any shells? I know there is a patch for ssh to log all commands from ssh sessions, but i want to log even commands executed from a ...
1
vote
0answers
27 views

Is there any considerations I should take when running untrusted apps as non-root user?

I have to use an application I don't trust (unstable) and I will run it as a non-privileged user so if something bad happens the damage would be limited to the home folder of that user. I removed ...
90
votes
8answers
14k views

Which is the safest way to get root privileges: sudo, su or login?

I would like to have the root account in safety even if my unprivileged user is compromised. On Ubuntu you can only use sudo for "security reasons" by default. However I am not sure it is any safer ...
0
votes
2answers
91 views

Execute scripts without decrypting them

I have a set of scripts (bash, ruby, python) and want to put everything into a container like file so I can deploy this container on a lot of servers. This scripts need to protect from accessing other ...
0
votes
2answers
89 views

SSH authenticity couldn't be established

Last night I SSH'ed to different systems.... one system/SSH reported that the "authenticity of HOSTNAME couldn't be established......." and it asks if I want to continue or something, I didn't and ...
0
votes
0answers
41 views

Use sudo as login

I've picked up the habit of using sudo and disallowing root logins. In cases, sudo is integrated with GUI configuration tools that require it. Are there any serious efforts to replace login and ...
5
votes
1answer
111 views

Is it safe for my ssh user to be given passwordless sudo for `apt-get update` and `apt-get upgrade`?

I have an SSH standard user account on my personal server, and it has sudo access (via its password). I ssh in using a public key, so I don't have to type in the account password to log in. Is it ...
2
votes
2answers
94 views

How can I allow SSH and SMTP only using IPTables?

I've got a raspberry pi set up to send me periodic emails. As it's connected to the internet 24/7, I need IPTables set up properly. I want to allow incoming SSH and allow emails to send out on port ...
1
vote
2answers
36 views

How can I create an SSH login that delegates to telnet securely

I'm playing around with the idea of creating a MUD, but one of the down sides is that they use "telnet" which is insecure. I'd like to retain the ability for "anonymous" users to access a specific ...
1
vote
1answer
28 views

Script samba password but securely

I want to script the addition on a samba user and the password. I have seen solutions similar to the one here Piping password to smbpasswd echo -ne "$PASS\n$PASS\n" | smbpasswd -a -s $LOGIN but ...
77
votes
6answers
49k views

Allow setuid on shell scripts

The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor: > cat setuid-test.c #include <stdio.h> #include <unistd.h> int ...
4
votes
1answer
39 views

Monitoring ARP Poisoning

How to monitor ARP poisoning? These few days my internal website that can be accessed locally has weird image replacing every images on the site for few seconds (it got back to normal after ...
11
votes
3answers
15k views

How can I block a range of IP addresses with an Amazon EC2 instance?

I know a certain range of IP addresses are causing problem with my server, 172.64.*.* what is the best way to block access to my Amazon EC2 instance? Is there a way to do this using security groups or ...
62
votes
20answers
10k views

Root access that can't change root password?

We are having a little problem on a server. We want that some users should be able to do e.g. sudo and become root, but with the restriction that the user can't change root password. That is, a ...
5
votes
4answers
4k views

Force Firefox to remember passwords on particular sites

Usually, when I log into a website with username and password, Firefox asks whether it should remember the login details. When I click yes, next time I visit the website, the username and password ...
11
votes
7answers
3k views

When does the Puppy linux security model make sense?

I have just spent a few hours playing with Puppy linux, which has some very nice features, but there are some things about its approach to security (at least the default settings) that worry me: It ...
1
vote
0answers
44 views

Allowing sudo kill for remote user for recovery purpose. Security implications?

I'm planning to create user allowed to SSH in and with right to sudo kill in case something disables local terminal/keyboard/display etc. Would probably add ps and/or htop to the list, as well. I ...
1
vote
2answers
106 views

Too many open ports in Debian 8

The IT department has given me 3 virtual servers with Debian 8 for my area, which I will manage (but they have some monitoring tools). Starting Nmap 6.40 ( http://nmap.org ) at 2015-05-11 13:33 ART ...
0
votes
1answer
44 views

What are the differences between sudo and the use of groups?

I know these are tools used for improving security. But what I would like to know is what they are and how they work?
20
votes
10answers
5k views

How to create strong passwords in Linux?

I wonder how I can create strong passwords on Linux (for both normal and admin users) and if there are specific programs to do that.
4
votes
2answers
116 views

how to prevent a buffer from swap

this question is specific to Unix and Linux. but it is programming and security, too. my program will get a clear password or decryption key by one of a few ways (decrypting a password file, asking ...
1
vote
0answers
31 views

Multiple DHCP Offers - Which is selected? [closed]

I have created a testing scenario in VMWare for a man in the middle attack using DHCP spoofing. It's for a college project. Windows 8 machine bridged to host adapter Kali linux bridged to host ...
6
votes
3answers
143 views

What bad things could happen if we don't use sudoedit?

We know it's safer* to use sudoedit, but what bad things can happen if we have the following in sudoers? Cmnd_Alias FOO = /bin/ed, /usr/bin/ed, /usr/bin/vi foouser LOCALHOST = NOPASSWD: NOEXEC: FOO ...
10
votes
1answer
344 views

D-Bus authentication and authorization

I'm trying to set up remote access to D-Bus, and I don't understand how authentication and authorization are (not) working. I have a D-Bus server listening on an abstract socket. $ echo ...
1
vote
0answers
86 views

Where to put the SElinux policy to allow acpid shutdown the system?

I'm using Centos7 minimal. I've installed acpid and the daemon is running. When I hit the power button, I get the following in /var/log/messages May 2 18:52:53 localhost systemd-logind: Power key ...
0
votes
1answer
228 views

Permission denied tmp dir on STIG RHEL

I am writing a program for a DISA STIG version of Red Hat Linux 6.5. I wrote a shell script to do self extracting on the program and when it self extracts put temporary files in the tmp directory that ...
0
votes
0answers
80 views

logging wrong passwords in /var/log/auth.log

/var/log/auth.log logs (among other things) failed login attempts to my debian linux. I was wandering if it is possible to ask it to log the password that was used in the failed attempt. This is ...
0
votes
1answer
394 views

SC_ERR_NOT_SUPPORTED(225) with Suricata on CentOS 6.5

I have just installed installed Suricata 2.0.3 RELEASE on CentOS 6.5. I try running it with sudo suricata -c /etc/suricata/suricata.yaml -i eth0 and get the following warning <Warning> - ...
-2
votes
2answers
42 views

Can I restrict the root to a single browser?

I want to be able restrict myself to firefox. I do not want to be able to use any other browser. So if I install chrome or any other browser, I don't want them to work on my Linux machine. Here is ...
2
votes
1answer
98 views

Understand HMAC authentication in case of site-to-site OpenVPN tunnel

I have a very simple OpenVPN setup where OpenVPN server is started with openvpn --ifconfig 10.10.10.1 10.10.10.2 --dev tun and client is started with openvpn --ifconfig 10.10.10.2 10.10.10.1 --dev tun ...
0
votes
1answer
43 views

What changes my boot partition and how to prevent it?

As an another countermeasure against security threats I wrote a little script that computes MBR and boot checksum and then compare it to the old one. As long as the computer is running this is OK, but ...
2
votes
0answers
88 views

Security of sudo not asking for a password after the first time

After using sudo and entering a password to do so, sudo remembers that we have entered a password and we do not have to enter a password the next time we use it. I am concerned about the possibility ...
81
votes
3answers
19k views

How do I recover from the Heartbleed bug in OpenSSL?

CVE-2014-0160 a.k.a. Heartbleed is a vulnerability in OpenSSL. It looks scary. How do I determine whether I am affected? If I'm affected, what do I need to do? Apparently upgrading isn't enough.