John Hesch

Have you ever tried accessing a website and it didn’t respond? Of course you have. We all have! Mr Uptime is an extension to your Firefox browser that will keep trying to reach that website in the background while you continue surfing on other websites. When the website is accessible again, Mr Uptime will let you know. You can also use Mr Uptime when a website responds but doesn’t load correctly.

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This is a fascinating look at how one person tracked down a hacker who broke into a buddy’s Linux server.

Whitelist For Exim Sender Verify Callout

Recently a user called and said that he was not receiving emails from a particular person. The email was being sent, but not received by the user. After verifying that the email was not getting caught up in a spam filter, I looked through the Exim logs located at /var/log/exim_mainlog. I found the email was being rejected with the error

could not complete sender verify callout

Exim by default, will check the senders email address and send a callback to the sending server to check and see if the users email address actually exists. In this case the senders email server was not verifying the email address actually exists and so the email was being rejected.

I didn't want to turn off callouts to verify the existence of email senders so I did some digging and found that Exim allows the callout feature to check with a whitelist to see if a callout instruction should be ignored. The instructions were locked within the cPanel forums which require registration and so my Google check didn't find these instructions.

I'm posting them here in hopes that others can find them easily. The original forum post is located here.

Create a file that will be the actual whitelist. In this example it is /etc/whitelist_senders - the addresses need to be listed one entry per line, either the email address or use the wildcard to do an entire domain. To create the file:

In WHM, in the top most edit box add (if there is anything else in the text box add this bellow it):

Still in WHM. scroll down to where there are three text boxes together. This is the begin ACL section. In the middle box scroll down until you find:

and change it to:

Still in the middle box scroll down to the end and change:

to this:

Save and exit. Now try to send and receive email to make sure everything is still working. If all is ok add the address in question to the whitelist and see if it works.

Then put the sender addresses in the file /etc/whitelist_senders, one per line, e.g.

If you're running a Linux server you better check to make sure you are ready for DST which comes early this year.

From the command line

zdump -v /etc/localtime MST7MDT | grep 2007

If you are in another time zone you will use one of the following.

zdump -v /etc/localtime EST5EDT | grep 2007

zdump -v /etc/localtime CST6CDT | grep 2007

zdump -v /etc/localtime PST8PDT | grep 2007

You should see

That's the date and time DST begins. If you see Sun April 1 you will need to update your system. Check here for information on how to manually update your system.

Digg dugg up this website with an ordered list of 195 free online programming books. If you look in the author's list of comments there are lots of other sources for free programming books as well.

Good site to bookmark.

Digg dug up a list of the Top 50 Linux Apps which turns out to be a pretty good list. Categories include games and entertainment, multimedia authoring, media players (audio and video), word processing and publishing, and basic productivity.

73% of respondents to a Compete survey said it is important that financial services providers keep them informed of important issues. 80% of respondents would like to be notified when their credit report is accessed, and 70% said they would like to be informed whenever their credit card is used.

So what is the problem? Why aren't financial institutions doing this?

VoIP-enabled cell phones inching closer to the market


New cell phones will use 802.11b/g as a backup to route calls over the Internet. I think this is awesome. Think about it, how many times have you been in an area where your signal was terrible? But, there is also a lot of talk about an increasing number of Internet service providers who are blocking third-party VoIP telephone services. The ISP's claim they are concerned about bandwidth but if that were the case they would be more concerned about P2P. A lot of these ISP's are also telephone service providers. Hmmm...

Instant Search was recently introduced by Yahoo which is similar to Google's Live Search. One cool feature is the weather search

I was dissapointed when I typed in 84770 movies only one theatre popped up. I tried typing in 84770 target and the Target store popped up with a link to a map. That was pretty cool. I have Google running through my veins so I don't see myself switching, but it's nice to have alternatives and good to see Ajax being put to good use.

Linux flaw could lead to DoS attacks


According to an advisory from security firm Secunia, a flaw has been found in Linux kernel version 2.6.x that could allow malicious local users to cause a denial of service attack.

Have you ever hit Ctrl-Alt-Delete and looked at the list of processes that are running on your PC? Processes run in the background keeping your operating system and other programs running. But some processes get left behind when a program has been uninstalled, or continue running even after the program has been shut down, and some processes are spyware or Trojans causing harm to your computer or private information.

I found ProcessLibrary.com today which is free online resource for anyone who immediately wants to know the exact nature and purpose of every single process.

Written in plain English, Processlibrary.com gives you immediate access to an extensive online database of comprehensive process description to help you understand what is truly running on your computer invisibly, in the background. The explanations are accompanied by exhaustive advice on whether you should terminate processes or leave them untouched.

ProcessLibrary even has a free program that plugins into your task manager called the Quick Access InfoBar. This program creates a small icon next to each running process in your task bar. Click on the icon and the corresponding web page opens with the details of the running process. Any questions you may have about a process that looks unfamiliar can be investigated easily and quickly.

I tried using the plugin on a couple processes running on my system but ProcessLibrary didn't have the process in their database. Of course I run a lot of obscure programs that most people probably never heard of. It's a great idea, especially if your system isn't running properly and you suspect a virus or spyware to be the culprit.

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A list of the best IM programs out there - from commercial and proprietary to open source.

This website provides several different options for connecting your iPod to you car stereo. First you select the type of iPod you have and then the make, model, and year of your car. They have solutions for over 10,000 different types of vehicles and car stereos.

Have you seen AjaxWrite yet? It's an amazing Web 2.0 type of application emulating an online version of Microsoft Word. You can load a Word document and use it just as if you had your Word application running on your desktop. Simply amazing.