Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.

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I have 300 Ubuntu 14 PC's that I block all internet except a whitelist - I do this by disabling dns, and have the central server do dns lookups for everything on whitelist and put it in a hosts file and have all the hosts use that. Obviously, this is a bit hacky but it worked.

The problem now - I have a need to whitelist *.slack.com. Slack says subdomains change too much, they cant provide a static list, or even a current list and then let me update it.

So I guess I need to enable DNS - what might be easy ways to still restrict to a whitelist of domains? I can easily run shell scripts on all 300 machines. (they check in with central server and grab a script and run it regularly). So anything I can install/configure via script is a viable option...

If it's not too hard I could set up an ubuntu machine to be a dns server.

Basically what I want is whatever is easiest so that I can just provide a whiltelist, that is allowed to have wild cards like *.slack.com and block everything else. I suppose it doesn't actually have to be a DNS based block if there is some client app.

Whatever it is, I am OK to set up a server myself - but the clients, it needs to be scriptable install/config.

I want to be able to update the whitelist easily/quickly.

Any ideas/suggestions?
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Hi,
what are differences between
user defined, environmental. local, global variables

when to use which one. what are advanatages, disadvantages of using each with practical examples.
please advise
0
Hi,

I like to write a unix shell script to check calendar year, date, current working directory.

how to write and shave .sh file(Say test.sh) and how to execute to see the output.

Any detailed link explaining these steps with screenshots. please advise
0
What are differences between
touch cat vi differences

which one is better to use to create a file. When to use which one. please advise
0
Hi,

I like to delete matched pattern in a file using vi editor and sed command

i tried as below not working

$ sed 'hello' aaaa.txt :% aaaa.sh


please advise
0
Hello,

I'm using Alienvault Ossim v. 5.3.79 together with ossec v. 2.8.

I'm trying to extend the following rules:
1002 - Unknown error somewhere in the system - bad words;
1003 - Non standard system message (size too large).

As these two rules give me a lot of false positive alerts, I've prepared custom rules in the local_rules.xml:
Original rules (syslog_rules.xml):

<rule id="1002" level="2">
    <match>$BAD_WORDS</match>
    <options>alert_by_email</options>
    <description>Unknown problem somewhere in the system.</description>
  </rule>

  <rule id="1003" level="13" maxsize="1025">
    <description>Non standard syslog message (size too large).</description>
  </rule>

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Custom rules (local_rules.xml):

<rule id="100002" level="0">
    <if_sid>1002</if_sid>
    <program_name>nfcapd</program_name>
    <match>Sequence Errors: 0, Bad Packets: 0</match>
    <description>False positive</description>
  </rule>

  <rule id="100003" level="0">
    <if_sid>1003</if_sid>
    <hostname>host1</hostname>
    <description>Ignoring 1003 from specified host</description>
  </rule>

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Unfortunately looks like above custom rules are ignored when I'm trying to use ossec-logtest:
For 1003:
echo "Apr 27 11:10:04 host1 user1[21565]: ./logtest.sh - Lorem ipsum dolor sit amet libero et lacus vestibulum vel, nibh. Fusce nonummy risus sit amet quam tempus vehicula, dui tellus, at lorem odio adipiscing at, egestas non, nulla. Maecenas in nulla quis 

Open in new window

0
I am conducting a penetration test against a fake Apache Tomcat server.  I have exploited the vulnerability in Metasploit and was able to open a Meterpreter session.  Some of my commands work with Meterpreter; however, commands such as "run hashdump" and "getsystem" return an error of this version of Meterpreter is not supported with this script.  I am running a virtual environment of Metasploit v4.10.0.  Is there any other script that can be used to complete this hashdump? Below is the exploit and payload that I used to open meterpreter:
use exploit/multi/http/tomcat_mgr_upload
set payload java/meterpreter/reverse_http

I have tried all other payloads that are are shown from the "show payloads" command.
0
Dear Colleagues,

I have a problem with executing SU command in Ubuntu 16.04.02. LTS.
The output is « -bash: /bin/su: Permission denied » (see attached screenshot).

Plz suggest something to overcome this issue.
ubuntu_terminal_error.jpg
0
Hi All,

Getting the above following message in my auth.log on my server from the above ip and many others ... what does this mean?

J
0
It is some type of Linux honey pot program. I was given a fife, honeymine.py, that is supposed to set the program up to to end to a SIEM to gather information on my internal network. Supposed to be installed on Linux Mint Mate 18. Classified as a "Low-Interaction" HoneyPot.

I have not been able to locate the installer or information more that I have given. Any help would be appreciated.
0
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Congratulations! You’re Certified – Now What?

Starting a new career can be overwhelming. Becoming certified in your field of expertise is a great start, but where do you go from here?  Here are some tips to help you on your career journey.

I want firefox to not erase cookies on browser close. I want to set this via a script. Below are gui based instructions for the goal settings.

Anyone know how to do this?

Thanks!

Firefox

At the top of the Firefox window, click the Firefox button and then select Options
Select the Privacy panel
In the History section, set Firefox will: to Use custom settings for history
Select the check box for Clear history when Firefox closes
click the Settings… button. The Settings for Clearing History window will open
In the Settings for Clearing History window, click the check mark box next to Cache.
Click OK
0
What is 'sticky session' when considering web traffic load balancing and how session-stickiness is usually achieved ?

can you please explain me a real world scenario. Like how it is used.
0
I am trying to set up a linux box as router ( packet forwarder to external + NAT). All the references I have found show that can be achieved using  iptables.
The question I have , if for performance  reasons  I can’t use iptables, is there any other alternative to achieve the same result ?

Thanks
0
Hi,
i'm looking for the quickest way to query Windows Event ID's from a Linux CentOS device.
I managed to do it via WMI but the enumerations of security logs using WMI simply takes too long.
what other methods are there to query Windows Event ID's as well as information from Active Directory using Linux?
can i use powershell from linux to query? how do SIEM devices like mcafee\greylog do it? what are the methods that can be done to query this info from linux other then WMI?

any help will greatly be appreciated this is driving me nuts
0
hi all,

I am now learning basic operation of Lunix and unix:

1) how to list active process in linux and unix and kill it accordingly.
2) how to change application start mode so that we can choose to start in administator/root user mode instead of general user mode in lunix and Unix.
3) how to check disk space left in linux and Unix.
4) what is the commonly use Linux and Unix administrative tools so that I don't need to use command mode?
5) how to check existing CPU usage of all CPU core in Linux and Unix, and therefore which application use the most CPU resource can be found.
6) how to check existing RAM usage of all application in Linux and Unix and therefore know which application use the most RAM/
0
Hi,

I want ot learn and practive Linux commands on my windows 10 laptop. how to instal and set up and practice in centos. please advise
I was checking below but not sure where and how to get software etc
http://www.tecmint.com/centos-6-3-step-by-step-installation-guide-with-screenshots/

please advise
0
Hello
Im new to Serverspec and LDAP and I was tasked to create some tests for testing and validating the infrastructure for LDAP is up and running correctly. Are there any good tests that I can code with ruby to validate that LDAP is running and configured properly?

Thanks!
0
Hello guys,
well i wanted to clear root password and admin password (sudo user) , using passwd -l root and then passwd -l admin, the result was successful
well my question how i can reset the password for admin only, knowing it keeps asking for current password which should be empty. no??
admin@mail:~$ passwd admin
Changing password for admin.
(current) UNIX password:

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whatever i try old password or enter for none, the result always failed.
what i'm missing in here? it shouldnt be empty already?

thanks guys
0
What is the easiest way to do this , do you have a sample kickstart file you can share with me that would have these options

thanks!!!!!!!!
0
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LVL 1
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I have a python script that copies some proprietary code from a USB to an app folder on a debian wheezy system.  The usb will be sent to a client site for them to plugin and click a button to do the update.  After the update is complete I use rm to delete the files from the usb but I assume this would be easily recovered.  I'm worried that the client will have this usb laying around and they will attempt to recover the files and have access to our code.

So the question is not of design, I know there are better ways to do it overall.  But in this case is there a simple way in python or using system.os to wipe or otherwise obfuscate the deleted files on the usb?  I can add your suggestion to the source code before we ship the usb (and test it of course)

thanks
0
Hi there
We are an MSP and cloud host. We would like to buy (or use) a web filter that we can provision in the cloud and offer to our clients to use it as a web proxy (if that’s the best way, perhaps) and be able to filter out objectionable content (with a warning issued to the end-user and the attempt logged and later reported upon to management).
The way I see it…
INTERNET  <----> cloud web filter/proxy <-----> client’s browsers forced to use the proxy
Importantly, the filter needs to be in the cloud (with a public IP) and NOT in the clients’ premises.
Ideally I would like to use an existing supported solution - either open source or paid, rather than roll-your-own from a Linux distro. I was thinking Untangle, SquidGuard, SafeSquid. Don't know if they can do it, or others.
Any ideas ?
Thanks
Michael
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I have Included the script.  This is a new install but the access_log is real and has values in it.  This script works on another instance without any problems.  The script reads the access log and counts how many times an ip hits the instance during a given time period.  It then sorts based on the highest hits at the top of the report via ssh.

Here is the message when it is ran
[root@ip-172-31-31-103 html]# ./modified_gawk.sh "26 Dec 2016" 06:00:00 "28 Dec 2016" 22:00:00
Examining from Mon Dec 26 06:00:00 UTC 2016 (1482732000)
            to Wed Dec 28 22:00:00 UTC 2016 (1482962400)

Processing /var/log/httpd/access_log-20161127 file

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This is an excerpt of the log file
77.75.79.72 - - [28/Dec/2016:22:00:41 +0000] "GET /robots.txt HTTP/1.1" 500 4596 "-" "Mozilla/5.0 (compatible; SeznamBot/3.2; +http://napoveda.seznam.cz/en/seznambot-intro/)"
77.75.79.72 - - [28/Dec/2016:22:00:41 +0000] "GET /category/vce/images/vce/20081117-fungusgnat.jpg HTTP/1.1" 500 4596 "-" "Mozilla/5.0 (compatible; SeznamBot/3.2; +http://napoveda.seznam.cz/en/seznambot-intro/)"
77.75.79.72 - - [28/Dec/2016:22:00:42 +0000] "GET /wp-content/uploads/wpcf7_captcha/1575611804.png HTTP/1.1" 500 4596 "-" "Mozilla/5.0 (compatible; SeznamBot/3.2; +http://napoveda.seznam.cz/en/seznambot-intro/)"
77.75.79.72 - - [28/Dec/2016:22:00:44 +0000] "GET /about/ HTTP/1.1" 500 4596 "-" "Mozilla/5.0 (compatible; SeznamBot/3.2; +http://napoveda.seznam.cz/en/seznambot-intro/)"
52.3.127.144 - - 

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0
Hi,

I am trying to set up a openLDAP (2.44) search/auth-proxy to a Windows 2012 R2 AD server on and off for a month now with no apperent success.

Third party applications need to search (verify) users against a LDAP connection in the DMZ. ( apps like like Proofpoint, etc.)

Has anyone have a good step-by-step guide for a newby or a OVA or similar?
(openLDAP 2.44 is not using SLAPD.conf, and all guides are still using that way of config...)

PS:I prefer it on a Debian based OS.....? :-)
0
Keep getting this error every time I add a password to a user.

[root@ip-172-31-31-103 html]# adduser ftpd2
[root@ip-172-31-31-103 html]# passwd 78AH832446X8e26W
passwd: Unknown user name '78AH832446X8e26W'.
[root@ip-172-31-31-103 html]# useradd -d /ftp/ftpd3 ftpd3
useradd: cannot create directory /ftp/ftpd3
[root@ip-172-31-31-103 html]# mkdir /ftp
[root@ip-172-31-31-103 html]# useradd -d /ftp/ftpd3 ftpd3
[root@ip-172-31-31-103 html]# passwd ^C
[root@ip-172-31-31-103 html]# passwd 78AH832446X8e26W
passwd: Unknown user name '78AH832446X8e26W'.
[root@ip-172-31-31-103 html]# useradd -d /ftp/ftpd4 ftpd4
[root@ip-172-31-31-103 html]# passwd RqQA64F5uQQR2AHs
passwd: Unknown user name 'RqQA64F5uQQR2AHs'.
[root@ip-172-31-31-103 html]# useradd -c 'FTP USER ftpd5' -m ftpd5
[root@ip-172-31-31-103 html]# passwd RqQA64F5uQQR2AHs
passwd: Unknown user name 'RqQA64F5uQQR2AHs'.

Open in new window

0
What is the syntax to test if a certain ip was included in a country block on an ipset on a Centos 6 server?
0

Linux Security

The Linux operating system, in all its flavors, has its own share of security flaws that allow intrusions, but there are various mechanisms by which these flaws can be removed, generally divided into two parts: authentication and access control. Authentication is responsible for ensuring that a user requesting access to the system is really the user with the account, while access control is responsible for controlling which resources each account has access to and what kind of access is permitted.

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Linux Security
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