PinoyTux Weblog » Tips

Tip: Can Download Torrents But Cannot Browse

Rai — Mon, 01 Sep 2008 04:14:39 +0000

I have recently purchased a new home office router that connects two desktops and one laptop by wireless connection. Back at the store, I made my mind to purchase Linksys WRT54G over D-Link (I forgot the model) because there are a lot of good feedbacks on Linksys.

Everything was good the first two weeks we were using the router. The signal strength is good and my laptop can get decent W-Fi signal anywhere inside. Then the network became rather choppy, pings are intermittent, and worst, one desktop (particularly my desktop PC) cannot browse.

The weird thing I was able to download stuff using torrent, my Pidgin can sign in to my accounts on Yahoo and MSN Messenger and streaming video and music works. Everything works, except for the browser. I blamed the Linksys for this and contacted the support thrice, and I was given a lot of configurations that should be done in the router settings, none of which solved my problem.

Googling around got me some help and apparently, this weird symptoms are caused by the traffic from torrent downloads. To fix this, these settings must be done on the torrent client:

1. Reduce the download and upload speed of torrent client. Since I use the lightweight uTorrent Client, I can simply do this by right-clicking the uTorrent taskbar and selecting the download speed that I want. The procedure could be different depending on your client.

2. Disable DHT. DHT stands for Distributed Hash Tables and disabling this in torrent client effectively solved my problem with browsing. Again in uTorrent, this can be done by pressing CTRL+P to open the Preferences window and selecting the BitTorrent tab. Uncheck the DHT selections and click OK to save the new settings. Restarting the client helps too.

I did these two steps and this solved the issue of not being able to browse the Internet while downloading torrents.

Tip: Hiding Files Inside An Image in Linux

Rai — Sun, 17 Aug 2008 02:34:42 +0000

I have a previous post on how to hide files inside an image file in Windows. If you have not read or watched the video yet, it is right here.

Anyway, a comment on that post gave a tip on how to do the same thing on Linux. Of course I tried it and it worked! According to Sebastian of mathemaniac.org, the concept here is really simple. An image file like JPG is read from the beginning of the file and terminated with an ‘End of Image’ marker. An archive file like ZIP has their metadata stored at the end of the file. Put them together and the image will be read as a valid image file and the appended ZIP file will be read as an archive.

Here is how to do it in Linux:

Get an image file and an archive of the files that you want to hide. In this example, I have cat beer_and_cig.jpg and hideme.zip file. The zip file contains an MP3 song that I have stored inside the archive. To create the archive-image file, run this command:

cat beer_and_cig.jpg hideme.zip > ucantseeme.jpg

What this does is the ‘cat‘ command reads the image file first, then reads the zip file and puts them together in the file named ucantseeme.jpg.

To test the integrity of the image file, try this:

# unzip -t ucantseeme.jpg Archive: ucantseeme.jpg warning [ucantseeme.jpg]: 4751 extra bytes at beginning or within zipfile (attempting to process anyway) testing: Feist - 09 - One Two Three Four.mp3 OK No errors detected in compressed data of ucantseeme.jpg.

Notice the warning message? The test saw that there were few bytes at the beginning, which means it saw the image file first but the archive is intact and no errors were found.

Perfect!

Tip: How Change Default OS in Dual Boot Ubuntu

Rai — Fri, 15 Aug 2008 13:29:31 +0000

My Acer 5570 Notebook is setup to dual boot Windows XP, for my online games and other Windows applications, and Kubuntu 7.10, my main operating system for stuff that I do most of the time like web browsing and blogging. Then my brother and I are now sharing the same notebook and he prefers Windows over Linux, not that I refuse to introduce him to Ubuntu but he had to use Microsoft Office for his office documents.

Windows and Ubuntu dual-boot systems are set boot Ubuntu first by default, so I decided to change the dual-boot order to default to Windows, since my brother will be using the notebook more.

To make Windows the default operating system in dual boot Ubuntu, follow these steps:

1. Press Alt+F2 to open the run dialog box.
2. Type in sudo gedit /boot/grub/menu.lst. Type in root password.
3. Edit the line that looks like this:

default 0

Change the number to the equivalent order of Windows in the operating system list in GRUB boot screen. The number 0 means that GRUB will boot the first operating system, and so on. If Windows is in the 4th line, change the number to 3.

4. Save the file and exit.
5. Reboot to check the change.

Windows should boot as default.

Tip: Perl script to Check Site Availability

Rai — Fri, 23 May 2008 08:00:32 +0000

System Administrators’s ‘common tasks’ are usually monitoring numbers of servers and network connections, and doing each monitoring is rather tedious. So to make our jobs and lives easier, we write scripts to automate repetitive tasks.

Since this is my Linux blog anyway, I decided to share one of scripts that I use in the office. This one is the Perl script that I use to check a specific site if the keyword is present, hence confirming that the site is up and accessible.

In this example I am using dattebayo.com’s parsing URL to test the script.

Dattebayo is one of the subtitling groups that provide fansubs of famous Japanese animes like Naruto and Bleach.

This script requires that you have the following packages installed:
- perl
- mutt
- sendmail or equivalent MTU

Please refrain from parsing the URL too many times or DB will ban your IP. Read their terms of usage here.

#!/usr/bin/perl -w

$get_url=”GET http://dattebayo.com/t/dump”;
$sidebar_list=`$get_url`;
$keyword=”Bleach”;
$date=`date +%c`;

#print $sidebar_list;

if ( $sidebar_list =~ /$keyword/ ) {
# print “Site is UP”;
# print $sidebar_list;
}
else {
`echo “Cannot Open Site. Check Server. \nTime Stamp: $date ” > text_mesg.txt`;
`cat text_mesg.txt|mutt -s “DB Site Error” “kamotegirl\@pinoytux.com”`;
}

Then put this in your crontab set to run every 2 hours so as not to flood the webserver with spurious requests (see above warning).

# crontab -e

Enter this line:

* */2 * * * /home/bom/shippuuden.pl (Change this to where you saved your script)

Save and exit.

Your shippuuden script is now set to run and send email to your address if the site is inaccessible.

Do you find this script useful or trash?

Tip: Simple SSL Certificate Scanner

Rai — Mon, 12 May 2008 10:44:15 +0000

If ever you need to write a script that needs you to scan the details of an SSL Certificate of a particular website, you can use this nifty one-liner to get the information that you need.

Security Certificates identify your site as a legit site and offers more secure connection by encrypting the data as it passes along the Internet highway. If the data is encrypted, chances are, the data being transmitted is less likely to be sniffed by malicious hackers.

If you manage hundreds of websites, each with its own SSL certificate that expires on different dates, you will need to create a script that will scan the certificates and capture the expiration dates and there is a nifty Linux command that can do this.

First step: Getting the CRT file.

To get the CRT file, use this command: (In this example, we will check the SSL of https://payperpost.com)

openssl s_client -connect payperpost.com:443

You will see a bunch of information, the same ones that can be found when you click the padlock icon on the browser, but what you are looking for is this:

—
Server certificate
—–BEGIN CERTIFICATE—–
MIIDSTCCArKgAwIBAgIDCEfCMA0GCSqGSIb3DQEBBAUAMFoxCzAJBgNVBAYTAlVT
MRwwGgYDVQQKExNFcXVpZmF4IFNlY3VyZSBJbmMuMS0wKwYDVQQDEyRFcXVpZmF4
IFNlY3VyZSBHbG9iYWwgZUJ1c2luZXNzIENBLTEwHhcNMDgwNDIyMTgzMzI0WhcN
MDkwNzIzMTgzMzI0WjCBuDELMAkGA1UEBhMCVVMxFzAVBgNVBAoTDnBheXBlcnBv
c3QuY29tMRMwEQYDVQQLEwpHVDYxNDEwMDQwMTEwLwYDVQQLEyhTZWUgd3d3Lmdl
b3RydXN0LmNvbS9yZXNvdXJjZXMvY3BzIChjKTA4MS8wLQYDVQQLEyZEb21haW4g
Q29udHJvbCBWYWxpZGF0ZWQgLSBRdWlja1NTTChSKTEXMBUGA1UEAxMOcGF5cGVy
cG9zdC5jb20wgZ8wDQYJKoZIhvcNAQEBBQADgY0AMIGJAoGBANYvXbe3oQy26gnL
H3wmPfmfzR5c0L5dCcBLkzqo8wJKVzlzlDgl6a9tFVJkotyoTJunI3qtwqmUeCQI
DyIqwnOdFDmTDm67PBn6315FN2xBvkf4ukmqBoJTjvuPuAY2Ye6xmhyMoJrN7uF5
ac2MR84y4VbuFGY5EIqd/bFCEOa1AgMBAAGjgb0wgbowDgYDVR0PAQH/BAQDAgTw
MB0GA1UdDgQWBBRN4gGXvUszrizghqxJpd+R6oKE6TA7BgNVHR8ENDAyMDCgLqAs
hipodHRwOi8vY3JsLmdlb3RydXN0LmNvbS9jcmxzL2dsb2JhbGNhMS5jcmwwHwYD
VR0jBBgwFoAUvqigdHJQa0S3ySPY+6j/s1draGwwHQYDVR0lBBYwFAYIKwYBBQUH
AwEGCCsGAQUFBwMCMAwGA1UdEwEB/wQCMAAwDQYJKoZIhvcNAQEEBQADgYEAqlQ9
b+6g2ZDW8O4gkDq/lNJfzY8wQrYGzunAZYxYtny2ejovFnz6DkMThNW8DmPNNv4P
dBikoICCh/8HM9luHcRbPAN0pycEF7FS7/leJ0egBm6G28we4XeBQQ+2AhAitUyZ
34BeotMGpw9vlwrleDtmUT6itncoYHp/Nt7TDyQ=
—–END CERTIFICATE—–

This is the CRT file and from this file, you will get the expiration date of the certificate.

Second step: Save the CRT file and scan.

Save the server certificate into a file, for example ssl.txt starting from
—–BEGIN CERTIFICATE—–
to
—–END CERTIFICATE—–

and you can use this command to extract the expiration date information from the file:

openssl x509 -in ssl.txt -enddate -noout

The result is:

notAfter=Jul 23 18:33:24 2009 GMT

Now you can use this information in your script so you can automate scanning of all your sites’ certficates.

—
220-601 as well as 70-620 are both prerequisites to the complicated SY0-101. This is one of the reasons why people try for 642-812 before sitting in the actual test, since the scores matter a lot.

Tip: How to Schedule Tasks

Rai — Fri, 02 May 2008 01:37:20 +0000

If you are using Windows, you are probably familiar with task scheduler to schedule certain tasks automatically. With Linux, tasks can be done on scheduled dates with cron.

cron is the service that works like task scheduler in Windows and can be used if you want to automate repetitive tasks like generating reports everyday or virus scanning. cron is handled by the cron daemon or crond, which should be running if you want your scheduled tasks to run.

Scheduling cron jobs are very simple. You just need to understand one teeny weeny line that comes with scheduling jobs. If you will take a peek at one of the cron files that exists by default on Linux systems, such as /etc/crontab, you will something like this:

# run-parts
01 * * * * root nice -n 19 run-parts /etc/cron.hourly
02 4 * * * root nice -n 19 run-parts /etc/cron.daily
22 4 * * 0 root nice -n 19 run-parts /etc/cron.weekly
42 4 1 * * root nice -n 19 run-parts /etc/cron.monthly

Now don’t get scared, it won’t bite. At least for now. Anyway, these lines are simple to understand and here is a breakdown:

Column 1: Tells the minute part of the schedule. (Values are 0-59)
Column 2: Tells the hour part of the schedule. (Values are 0-23)
Column 3: Tells the day of month part of the schedule. (Values are 1 -31)
Column 4: Tells the month part of the schedule. (Values are 1-12)
Column 5: Tells the day of the week part of the schedule. (Values are 0-7, 0 is Sunday)
Column 6: Tells which user will execute the command.
Column 7: Tells the command that will be run.

So, a simple task that we could run to test our cronjob is to to create a test file and update its timestamp everytime the scheduler runs. We could do it like this:

30 15 * * * root touch /root/cron-test.txt

The ‘touch’ command will run once a day, every day at 3:30PM. What the command does is it will create a file if it doesn’t exist and will update its timestamp if it already does. This we will know if the task was executed if we see the file named as /root/cron-test.txt.

Once a day seems a little too long to wait so we should run the task every 15 minutes so we can see the timestamp updated by doing this:

*/15 * * * * root touch /root/cron-test.txt

This will run the task every 15 minutes for the rest of the day, everyday. If set to this, you should see the timestamp of /root/cron-test.txt updated every 15 minutes by doing ls -l command.

Of course you can do so much more with crond except updating timestamps on empty file. One good example is to create an archived backup of your home directory every day. However, this task could need a little bash script.

Hacker’s Black Book

Rai — Tue, 22 Apr 2008 03:01:21 +0000

Being a systems administrator, it my job to deter mischievous users who plans to cyber-attack any of our servers and boy, it is easier said than done. Hackers are always a step ahead and a vulnerability will attract malicious hackers into your innocent server like ants to sugar. And so I purchased a book that will help me understand a little more about hacking.

I have a personal copy of Hacker’s Black Book and it is one of the best hacking books I have ever read. It is straight to the point, no nonsense book with actual examples and not just theories about hacking. It also comes with a CD containing over 100 hacking and security tools, which is very useful if you want to know more about hacking activities.

This book is not intended to be used for attacking a certain website or server, but as an informative tool so we can know more what hacking is about and how to prevent it. Hacker’s Black Book is very cheap compared to other books on the market, a very good value for your money.

If you are interested to learning more about hacking and protecting yourself against malicious hackers, you can visit the official website by clicking the link on the right.

Stop Identity Theft Now

Rai — Mon, 14 Apr 2008 19:25:25 +0000

Since the beginning of Internet, securing personal privacy is always prioritized. Information is always available when we need it but other people also has access to the same information. Then comes identity theft.

There are numerous cases of identity theft all over the world. Hollywood movies are even made about these cases and though they are just movies, they can happen in real life.

So what is identity theft?

Identity theft happens when someone uses your personal information and assumes your identity. Sometimes the information they use is available online or they got hold of your mails such as credit card statements. This can happen to anyone at any time. You may not even know it.

What can we do to prevent this?

There are some basic steps to prevent your identity from being stolen like shredding your documents like bank accounts statements before you throw it out. Also, there are companies like Lifelock that offer a proven solution to prevent your identity from being stolen. Their proven method saves you thousands of dollars from fixing the mess of identity theft.

Lifelock will insure that you will remain protected as long as you are a member. But in the unfortunate event that your identity is compromised, they are willing to fix it for you even if it means costing them a huge amount of money. They also work with some companies like US Airways and Ident-A-Kid, providing identity protection solutions for their customers.

If you are interested with working with Lifelock, Lifelock jobs are available to those who are willing to grow in a challenging environment and diverse workforce.

Identity theft is a serious issue. It takes time to recover and get back your good reputation, not to mention very expensive. So don’t take any chances and start evaluating yourself if you are a highly potential victim.

Tip: How to Delete Files with Special Characters

Rai — Sun, 13 Apr 2008 10:06:52 +0000

How to delete files with dash or any special character?

Have you tried to delete a who-knows-where-it-came-from file which has a special character like preceded with dash or question mark? I bet that when you tried to delete it, you got something like this:

[root@rai01 home]# rm -ucantdeleteme
rm: invalid option — u
Try `rm ./-ucantdeleteme’ to remove the file `-ucantdeleteme’.
Try `rm –help’ for more information.

Now what?

The reason behind this is because the rm command is treating the dash (-) as an additional parameter or option. So since -ucantdeleteme is not a valid option for rm to use, but a file, the rm command returns an error.

One trick that I always use to get around this is to tell the rm that you are referring to something that is a file. You can do this by adding ./ before the filename, like so:

[root@rai01 home]# rm ./-ucantdeleteme
rm: remove regular empty file `./-ucantdeleteme’? y

Voila! You can now delete that pesky file. You can also do this to files with ? in their filenames.

Lizard Safeguard Protects Your PDF Files

Rai — Thu, 10 Apr 2008 07:35:19 +0000

In this age where documents are passed through wires and fax machines are nearing extinction, it is important to protect your valuable information from prying eyes and unwanted readers. That is why password-protecting have become a standard procedure in PDF DRM document security to protect documents that are confidential in nature like a restaurant’s secret recipe or business trade secrets.

Though it is true that layering passwords over PDF files provides a sense of security, it is not enough. After all, a password is just a simple way to control access to your confidential document. Nevertheless, LockLizard’s Safeguard PDF Security provides a tougher protection for your PDF files.

Lizard Safeguard PDF Security allows you to have control over and provides protection for your files more than a simple password can. With very little effort, you can control who gets to read the document and you can also set how many times a document can be viewed, copied or printed. You can set expiration dates for your document as an added layer of security or revoke someone’s access rights to prevent further viewing or copying of the document.

Lizard Safeguard PDF Security is a simple and versatile tool that offers more than just a basic password protection for your intellectual property and lets you have control over your own documents. Knowing that your PDF files are protected by Lizard Safeguard PDF Security, you can be assured that you are not putting critical information at risk.

Discount Tech Products

Rai — Sun, 06 Apr 2008 14:42:13 +0000

If you are looking for ways to get discount on items you wish to purchase, one way of getting this is to look for bargains and discounts offered by online stores like newegg.com or ebay.com

Promos and discounts are not very hard to find if you know where to look for. Most online companies offer big discounts when you subscribe to their mailing list. There are also times when some third-party companies give free coupons to online shoppers. Some coupons can also be printed and be brought to the store if online shopping is not an option.

Just remember to always look for the secure site signs like SSL certificates when doing online shopping to protect your personal and financial information.

Using Internet as Alternative to Malls (1)

Site Uptime Checkers

Rai — Tue, 01 Apr 2008 17:40:01 +0000

To those who need to check the availability of their sites across the world, these are some of the handy tools that I use.

Why check site availability from multiple locations?

We all know that DNS propagation varies depending where you are located. So in some cases, a site may be accessible from California, but not in London. Using these tools, you can verify which locations can access your site.

1. Alertra - Alertra lets you check your site from multiple locations to make sure that your website is not only accessible from where you are now, but also from somewhere else on the planet. You can choose to use their free service called Spot Check, which checks one site at a time. You can also subscribe to their full service which includes downtime report and sends alerts if your site is down.

Sample result:

SpotCheck

URL: pinoytux.com

Timestamp Location Result Size Time
2008-03-27 16:25:24 EDT Shanghai CHINA OK 50.9 16.31
2008-03-27 16:25:24 EDT Hong Kong CHINA OK 50.9 14.73
2008-03-27 16:25:24 EDT Frankfurt GERMANY OK 50.9 13.11
2008-03-27 16:25:24 EDT Sydney AUS OK 50.9 12.99
2008-03-27 16:25:24 EDT London UK OK 50.9 11.66
2008-03-27 16:25:24 EDT Orlando USA OK 50.9 11.41
2008-03-27 16:25:24 EDT Las Vegas USA OK 50.9 10.59
2008-03-27 16:25:24 EDT Atlanta USA OK 50.9 10.52
2008-03-27 16:25:24 EDT Chicago USA OK 50.9 10.19

2. SiteUptime

SiteUptime offers free site monitoring service but restricted to one site only. Sites scanned by SiteUptime are scanned from four different locations and sends alerts if site is inaccessible. This makes sure that your site is up and you will not have to worry about losing visitors while your site is down. There are also paid services that are available which offers more features for your account.

Quick check for: pinoytux.com (http)
Date City Country Time (s) Result

Average Response Time: 0.457 seconds

3. Keynote Red Alert

Keynote Red Alert is an extensive site checker which not only checks the site and its pages, but also monitors the device where the site is hosted. You can opt to monitor the device where Red Alert sends pings to the server and if the server fails to reply, it will send alerts by pager or email. Red Alert can also monitor other services like SMTP and SSH, making it an all-in-one monitoring service. It offers free trials to those who are interested in purchasing their services.

4. Down For Everyone or Just Me

No nonsense, quick site checker. Checks from single location though.

It’s not just you! pinoytux.com looks down from here.

5. Host-tracker

Host-tracker can also give you a free one-site-at-a-time checker from different locations called ‘nodes’ and as of this writing, they have 63 nodes that will check your site accessibility. If you require more than just site uptime check or checking at specific intervals, you may want to subscribe to their paid services.

Location Result Page Size Response time Kb/sec IP Partner

Received responses: 31 Ok Average: 8.93 sec 5.51

SPb, RU Ok 50351 6.49 sec 7.57 69.80.227.79 TimeWeb
SPb, RU Ok 50351 6.49 sec 7.57 69.80.227.79 TimeWeb
Canyon Country, CA, US Ok 50351 2.82 sec 17.41 69.80.227.79 HostIran Networks
Kiev, Ukraine Ok 50351 6.80 sec 7.23 69.80.227.79 HOSTED

Remember that site availability is one of the considerations that search engines like Google checks. So if your site is often down than up, maybe it is time to switch hosting providers.

Tip: Perl script to Check Site Availability (0)

PinoyTux Weblog » Tips

Tip: Can Download Torrents But Cannot Browse

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Tip: Hiding Files Inside An Image in Linux

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Stop Identity Theft Now

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Tip: How to Delete Files with Special Characters

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