Category: Computers

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ssh-vulkey : How to test weak SSH keys on your server

This might be stale news by most security alert people, but I felt compelled to write this post nevertheless. Byy this time most security alert people have realised that a serious security vulnerability has been discovered in the random number generator used by OpenSSL on Debian and Ubuntu systems, and there are a lot of sites have published information about it. [1] [2] [3] [4] [5].

This vulnerability caused OpenSSL to generate “common” and predictable keys, which is easily crackable by using brute-force algorithm. In the extreme case, some of the keys are successfully cracked in 2 hours time. Longer keys 8192-bit RSA keyset might take as short as 129 days to generate as opposed to hundred of years if the keys were generated securely.

Which Ubuntu Linux system are affected ?
As Ubuntu linux operating system is based on Debian, it inherited Debian vulnerability problem. Users who has generated keys under (before updating to the new OpenSSL package via automatic updates, which is before May 13 2008) — Ubuntu 7.04 Ubuntu 7.10 Ubuntu 8.04 LTS are all affected by this vulnerability

Other system which uses the keys generated by Debian and the above mentioned Ubuntu system is also affected as the keys might allow malicious 3rd party user to abuse the system. SSH login which uses these keys will not be considered secure anymore, and are advised to update their SSH keys immediately.

How to check against weak SSH keys ?
A system is as strong as its security measures (in this case, the key) to protect it. By using ssh-vulkey as detailed in Ubuntu Security Notice 612-2, you can detect weak keys in your system, and updates them accordingly.

Run “sudo ssh-vulnkey -a” command to check against weak keys :

ssh-vulnkey -a

ssh-vulnkey -a
Not blacklisted: 2048 fa:2e:1d:a6:84:64:a1:80:c4:31:68:5a:b0:1a:cb:fe /etc/ssh/ssh_host_rsa_key.pub
Not blacklisted: 1024 f4:34:04:85:58:a0:6b:0a:a1:b9:2d:3b:e6:19:5a:76 /etc/ssh/ssh_host_dsa_key.pub
COMPROMISED: 2048 5c:10:8a:c0:55:8c:1f:d9:4b:05:f0:35:0a:0d:2f:5c /home/someuser/.ssh/authorized_keys
Not blacklisted: 2048 a7:b4:3e:41:18:cb:f7:68:5e:4f:ae:30:14:d2:17:fd /home/someuser/.ssh/authorized_keys

More information about OpenSSL in Debian / Ubuntu security vulnerability :

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OpenOffice- Howto Print Multiple Slides (Handout) in One page

There are times when you want to print multiple presentation slides in one page, especially when you are making handouts to give away to your audiences. Here’s how you can do that easily using OpenOffice.org Impress.

First click at the “Handouts” tab.

Printing Multiple slides on a single page in OpenOffice.org

Then you will see the slides arranged on a single page. Typical number of slides is usually between 4-6 on a single page. You can select layouts option to determined the number of slides.

OpenOffice Handouts

Alternatively, you can change the page layout to to Landspace to give it a “wider” feeling to your handouts. Just right click and select Page Layout.

OpenOffice Handouts

OpenOffice Handouts

Finally you can print your handouts by selecting File->Print, and clicking Options at the bottom of the Print Dialog. Select Handouts, and print the documents as usual.

How to print OpenOffice Handouts Slides

That’s all, hope it will help you in your daily works.

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Beware of the Fake GMail Administrator email

GMail users, a word of warning, I’ve discovered a new phising email designed to steal your Google account password and credential.

Here’s how the email looks like.

Fake Gmail email

Fake Gmail email

Gmail users are advised not to fall into these type of scam as the scammer can use your Google account for all sort of nasty things. Please change your Google Account password as often as possible

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FLV2MPEG4 : Convert FLV to MPEG4

Here is an easy way to convert Adobe Flash Video files (FLV) to MPEG-4 using a tool called flv2mpeg4.

  1. First you need to download flv2mpeg4 using svn from its project websites

    svn co https://vixynet.svn.sourceforge.net/svnroot/vixynet/trunk vixynet

    .

  2. Install ffmpeg, libavcodec-dev, libavformat-dev and libavutil-dev package
  3. read the docs and compile flv2mpeg4

You can convert flash video file to mpeg4 by executing :
flv2mpeg4 youtube.flv youtube.mpeg4

Alternatively you can install flv2mpeg4 from GetDeb.net website.

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AVTech CCTV DVR Motion Detector Settings

Couple of days ago I was given a task to configure CCTV DVR device (AVTech 4 Channel MPEG 4 recorder). I prefer the embedded device approach as opposed to the cheap PC CCTV cards as the latter requires a full blown PC and it depends on Windows operating system (which naturally incur additional costs).

AVTEch CCTV Security DVR

The AVTech CCTV DVR is priced slightly higher, but you get the perks of having a dedicated and compact device for your CCTV solution. It has a network interface which lets you configure and view your CCTV security camera over the internet.

Motion Detector Settings
Generally I’ve no trouble at all in using AVTech, the only thing that I’ve hard time figuring is the motion detector settings, which allows the camera to record the video only if it detects movement on one of its cameras.

Fortunally I found a source which reveals the meaning of each configurable settings on the AVtech CCTV device :

Continue reading “AVTech CCTV DVR Motion Detector Settings”