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Geoffrey Chapman - Macrotone Blogs - Page 13

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Geoffrey Chapman
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An IT professional with a wide experience of IT systems, specialising in Database Management and Security.

Geoffrey Chapman

Private IP addresses visible on Internet?

This should not happen, BUT we have observed a few private IP addresses being used by visitors to our site.

An IP address is considered private if the IP number falls within one of the IP address ranges reserved for private uses by Internet standards groups. The following  private IP address ranges exist:

      10.0.0.0 to 10.255.255.255
      169.254.0.0 to 169.254.255.255 (APIPA only)
      172.16.0.0 to 172.31.255.255
    192.168.0.0 to 192.168.255.255

These private IP addresses are (normally) used on local networks which includes homes, schools business LANs etc.  Devices with private IP addresses cannot (should not be possible to) connect directly to the Internet. Similarly devices outside of the local network cannot (should not be able to) connect directly to a device with a private IP.  Typically access to such devices are brokered by a router or similar device that supports Network Address Translation (NAT).  NAT effectively hides the private IP numbers but can selectively transfer messages to these devices, affording a layer of security to the local network.

Standards groups created the private IP addressing to prevent a shortage of public IP addresses available to Internet service providers and subscribers.

So given that these private IP addresses should not be visible on the Internet, how is it possible therefore for our site to have recorded access from devices with addresses in the 10.x.x.x and 192.168.x.x ranges? 

One can always block these devices from access to web pages by including the private address ranges within ‘blocked’ ranges, using commonly available tools available upon the web, but it still doesn’t explain how there are visible in the first place! If in doubt it is possibly wise to block them as a matter of course for a site on the Internet. Remember if the site is on a ‘local’ LAN that blocking them is not an option.

One wonders if there is a connection with the implementation of IP v6, and whether somehow these address ranges are getting through.  Alternatively perhaps a particular NAT provisioning mechanism is faulty?  Another possibility is that  dubious entities are using them to ‘mask’ their activities.  We are led to the latter possibility since the 10.x.x.x devices were attempting access to our site ‘back end’.

Despite some extensive searching we do not currently know the source of these connections, which raises a few possibly serious security concerns. We will continue our investigations.

Tags:
security Privacy Communications
Geoffrey Chapman

Doing more with LESS.

http://lesscss.org/images/logo.pngAs part of our ongoing work on our Joomla components we have been looking at the ‘next’ logical change that we want to implement with the CCS styles.  This is of course making use of the LESS compiler.

What is LESS you might ask.  Well LESS is a dynamic stylesheet language, which extends CSS with dynamic behaviour such as variables, mixins, operations and functions.  It can run upon both the server-side or client-side (modern browsers only) on a site.

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Tags:
browser developers
Geoffrey Chapman

Web Standards

   I am reminded of the quote “The nice thing about standards is that there are so many of them to choose from.” attributed to  “Andrew S. Tanenbaum”, whilst looking into the structure of web pages.

The Firefox browser add in ‘FireBug’ provides a nice tool under ‘Tools- Validate HTML’ which enables the page one is viewing to be checked by the W3C Markup Validation Service.   By default it uses the standard defined at the start of most web pages, but the number and variety of possible standards is most interesting.  The output is a nice listing of ‘errors' and ‘warnings’ upon the page structure and its elements. [Note that it excludes the ‘new’ standards mentioned below, although it does have ‘HTML5 Experimental’]

Whilst one can then proceed to correct and eliminate the errors and warnings it does raise the question as to what standard should one be writing web pages to:  HTML5, XHTML 1.0 Transitional, XHTHL 1.0 Standard, XHTML 1.0 Framework, HTML 4.01 Strict etc.  The list goes on to provide about 15 possible standards.

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Tags:
Tools Javascript browser compliance regulations
Geoffrey Chapman

Problem accessing some sites and HTTPS Everywhere.


We have noticed a small problem recently when trying to access a specific site ‘www.joomla.org’.  Not a particularly unusual place to access given some of our work. What was confusing was that other sites in the same domain were all accessible.

After much head scratching and trial and error, clearing cache’s and disabling cookies etc.  we eventually discovered the cause.

We use an extension names HTTPS Everywhere in our Chrome and Firefox browsers and it was this that was forcing the use of the HTTPS protocol on the site.  The result was that the site was always timing out.  Once identified the resolution was (as usual) simple, and involved disabling the use of HTTPS for that specific address.  Once this was done the problem was solved.

This type of problem may of course impact other web addresses, but after six months of use we must admit it is the only site that has every given us any problem. One for others to note in case they have the same type of problem.

Geoffrey Chapman

SPAM and IP blocking

spamSince we started mapping IP addresses of persistent attempts to submit SPAM on our live site, it is obvious that Miami in the US is one of the most persistemt source. Already even though it is only the fourth day of the month we can see 128 attempts to submit SPAM messages.

This is annoying since it just increases the size of the server logs that are inspected for system problems and adds a lot of background noise.

I have decided therefore to start blocking the persistent IP addresses being used. The effect is virtually immediate with the incidences which were occuring very 5 minutes or so having ceased. It is a pity that some individuals feel the need to insert advertisements for 'personal' products on sites where they are totally inappropriate.

We therefore apologise to anyone inadvertantly who may be refused site access because they are given an IP address in our blocked range.  If you are caught then please contact support who will investigate and if necessary 'unblock' the IP address.

Tags:
SPAM
Geoffrey Chapman

Farewell to Microsoft Messenger

With the imminent demise of Microsoft Messenger (25th March 2013), which we have used for a number of years without any problems, we have made the upgrade to using Microsoft Skype.  This being the product that Microsoft brought in and has decided to replace the ‘old’ Messenger service.

The upgrade went clean enough and the ‘old’ Messenger software was successfully uninstalled.. Now to see how it measures up.

Noticed the upgrade tried to ‘push’ the use of Bing, and MSN as a homepage in the browser, which can be easily overlooked, but somehow one expects that!

Now to see how it works in practise.

Addresses etc. remain unchanged, so current contacts should all continue to work.

Geoffrey Chapman

Experiences using DocBook XML

This summaries a few of the lessons learned using DocBook XML for documentation.

Upcast: The conversion from Microsoft Word to DocBook XML introduced a few opportunities for changes:

1. Media objects (figures) are all converted to ‘inlinemediaobject’, and even when the image is on its own it always is surrounded by ‘para’ and results up positioned on the left hand side of the page. The best approach we found was to convert them to simple ‘mediaobject’ and change then to become ‘figures’ and in this way also enable the creation of a ‘List of Figures’. We also tended to change the specified exact image size to use scaling so that the width of 14cm was most appropriate. [This did impact the fact that all html screen images come out at a standard width.]

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Tags:
XML documentation DocBook
Geoffrey Chapman

DocBook XML to PDF

The Apache FOP ProjectThe next stage in our documentation changes was the creation of PDF documents from the DocBook XML formats.  [See previous posts for other blogs on our documentation changes.]

There is a need to use a XSLT transform to convert the XML document to a FO (formatted object) which can then be processed to create the PDF output.

The DocBook distribution have available a set of XSL transforms for converting the XML files into a variety of different formats, so the first step was to download these. This is not strictly necessary since it is possible to access the XSL transforms over the web, but having a local copy speeds up the transformation process.

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Tags:
DocBook XML Tools developers
Geoffrey Chapman

Custom CSS and DocBook XML documents

docimport-48We have previously mentioned using XML documents in DocBook format. We now turn our attention to the question of the format of the tables. A previous blog on DocBook table format mentioned the two types of  tables supported by DocBook, but not every document table necessarily has to be in the same format. We have an ‘in-house’ style used for some time and the desire was to retain a similar format with our web pages.

We are using a Joomla component named DocImport written by Nicholas K. Dionysopoulos and are very pleased with its behaviour even though it is still in an ‘alpha’ release form. A credit to the authors abilities. The component presents each web page with headers and footers which are using a ‘table style’ which does not display column separators. This is understandable since the standard format for tables is basic to put it bluntly. 

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Tags:
XML tables documentation DocBook
Geoffrey Chapman

Animated Gifs in banners stopped working

lg-1and1
Noticed a little while ago that the banner we use for our affiliate link to 1&1 Internet was not being displayed in our page footer.

Further inspection revealed that 1&1 Internet had changed their affiliate specification slightly (not that we were informed but there you are!).  Anyway they now provide animated GIFs to use so replaced our 'old' configuration with the suggested new details.

That was fine apart from the link still refused to display. So we had to investigate further. What didn't help was that we were unsure exactly when the link first exhibited problems, so were unsure whether this was caused by a change of ours, or just by 1&1.

To cut a long story short, we discovered that it was the animated GIFs that were causing the problem, since a static image displays fine. For our purposes a static GIF is fine, and until we have more time to see if the animated GIF problem is more widespread than just banners it will suffice.

Tags:
joomla images
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