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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0
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2answers
35 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 ...
74
votes
6answers
45k 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 ...
0
votes
1answer
19 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 ...
4
votes
1answer
32 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
13k 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 ...
2
votes
2answers
575 views

securely automating a script which requires a key to do its task

I have a script that downloads bank transactions to store in a database. To get these transactions requires a password for each account. The database is encrypted and requires a key to access it. All ...
62
votes
20answers
9k 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 ...
2
votes
2answers
901 views

AIX 6.1 — Without root can I get the last failed login for a user i have access to?

I know the information is in the security files but I don't have access and it's more work then I want to do to go to our Unix admins to get the information (everytime the account gets locked which is ...
5
votes
4answers
3k 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 ...
37
votes
4answers
6k 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 ...
4
votes
0answers
83 views

Unexplained files found in home folder

For background information, I'm running openSUSE 13.2 and KDE 5. Today I found a number of unexplained files and folders in my home folder which state they've been edited 3 days ago. I do not ...
1
vote
0answers
22 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
49 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 ...
1
vote
2answers
37 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 ...
0
votes
1answer
40 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?
19
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
99 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 ...
5
votes
1answer
552 views

gdm greeter configuration: Exclude all *except* for one specific user

I have Googled this one and tried so many combinations, with no success. I need the GDM login greeter to display one and only one username. In effect, what I need is something like this in ...
1
vote
0answers
16 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
126 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 ...
2
votes
1answer
324 views

Hiding an encrypted folder in a shared system without root access (unshare -m)

I'm a graduate student trying to use a cluster at my university. These machines are shared, so I want to protect the source code I use (I signed a NDA, so I'm scared about publishing the code by ...
10
votes
1answer
129 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
24 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
196 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
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0answers
38 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 ...
1
vote
1answer
568 views

Make bluetooth device invisible / disable incoming pairing

I am using the bluez package for my bluetooth usb dongle on ubuntu server. I want to be able to initiate bluetooth connection from the dongle to a device, however a device itself shall not be able to ...
0
votes
1answer
298 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
41 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
30 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 ...
47
votes
2answers
1k views

Security implications of forgetting to quote a variable in bash/POSIX shells

If you've been following unix.stackexchange.com for a while, you should hopefully know by now that leaving a variable unquoted in list context (as in echo $var) in Bourne/POSIX shells (zsh being the ...
0
votes
1answer
30 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
73 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.
2
votes
1answer
151 views

Exploit FOUND with clamav on Fedora 21 in Oracle's java

I'm scanning one of my systems with Clamav like this: $ clamscan -r -i --remove --max-filesize=4000M --max-scansize=4000M \ --exclude=/proc --exclude=/sys --exclude=/dev ...
0
votes
1answer
66 views

How can I study Linux, in and out? [closed]

My team and I will soon begin studying and practicing for the nation-wide Cyber Patriot program. As I'm famed for being our "Linux guy", I would really like to improve my knowledge on the subject. ...
1
vote
1answer
32 views

Where to verify and review various packages before installing them

I am new to Unix/Linux and corrently setting up a Debian Wheezy server for my domain name. Here and there I find useful tutorial on how to do this-and-that, but I am not sure where I can find a ...
4
votes
2answers
109 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
1answer
46 views

UNIX Account management

Would like to know if there's some opensource solution aimed to manage and administer system authentication and RSA keys for staff, contractors and clients across the organization. My systems to ...
2
votes
1answer
53 views

How to scan a directory with a space in its name with maldet

I'm trying to scan some directories with Linux Malware Detect (command-line command maldet): maldet -a /SOMETHING\ 1/ But I get: maldet(13857): {scan} invalid path /SOMETHING 1/ I've tried ...
1
vote
1answer
825 views

Any better alternative to chroot on an OpenVZ VPS?

Are there any better alternative to chroot environment? I'm thinking about running nginx on a jailed environment. BTW, I'm on OpenVZ VPS, so modifying the Kernel is a no-no. (I think that prevents ...
3
votes
3answers
117 views

Remove passphrase from private key and set specific file mode

If I set a passphrase on my private key like so: openssl rsa -des -in insecure.key -out secure.key and I remove the passphrase like so: openssl rsa -in secure.key -out insecure.key then my ...
1
vote
1answer
54 views

wheel groups and permissions

I'm new to a lot of things Linux, so this might be basic stuff. We're thinking about setting up a wheel group and removing permissions from root. Not even sure that's possible. We are having a ...
1
vote
1answer
399 views

Unable to set capability CAP_SETFCAP by user

The question is about capabilities. I need to allow user to set capabilities using setcap. When I call it by root all goes fine, eg $ sudo setcap cap_dac_override,cap_dac_read_search+ep ./bin_file $ ...
0
votes
1answer
26 views

Sanitise bash arguments

I have a script which takes user input and does a lot of things. One thing which I am worried about is it takes a file name and removes that file. e.g. rm -rf $arg1. A user could technically input / ...
6
votes
1answer
142 views

When running 'su - username', pam_group doesn't add additional groups from /etc/security/group.conf but sshd login does?

I am having trouble determining why su doesn't behave as the PAM configuration would imply. In short, using su to become another user should load secondary groups according to PAM configuration, but ...
4
votes
1answer
104 views

SSH server listening on multiple ports with passwordless access not allowing connections to second port

I have my Synology NAS running an SSH server listening on the default port 22 and I set up passwordless authentication with a public/private key and a passphrase: From sshd_config: ...
5
votes
2answers
449 views

Myth or reality: SELinux can confine the root user?

I read or heard somewhere (maybe in LinuxCBT's SELinux course; but I'm not sure) that there are online Linux servers, for which the password of the root user is also given. The Linux server is ...
0
votes
1answer
172 views

How to import the official Tor GPG keys?

I am trying to install the latest Tor Browser Bundle on Arch Linux: $ makepkg --syncdeps --install [...] ==> Verifying source file signatures with gpg... tor-browser-linux64-4.0.8_en-US.tar.xz ...
1
vote
1answer
38 views

LDAP Force Password Change Through HTTPS

We have a "master" server running Suse Enterprise with LDAP that controls user's access to our systems. We want to implement a 90 day expiration policy, but the issue is that most of our servers are ...