It's quite a worrying time in Bangladesh at the moment, there are threats not only from terrorism but general unrest throughout the country. At the moment the UK Government is advising against all travel to the Chittagong Hill Tracts and most other Western Governments have similar advisories in place.
Yesterday (23rd Nov) there was a countrywide strike and there is a violent feel of unrest in the air in many places. Last week there was another terrorist attack against an Italian priest, which was reportedly claimed by ISIL. The target was 57 year old Piero Parolari, who was gunned down whilst cycling to a catholic missionary hospital where he worked as a doctor, fortunately he survived although he has suffered serious injuries.
There are problems from the civilian population too, particularly supporters of the Jamaat-e-Islami party who are organising protests to support two former leaders who face the death penalty in relation to crimes committed in the 1971 war of independence against Pakistan.
So in a classic, not sure what to do over reaction, the Government has instigated a block against a variety of social networking sites. Facebook has been blocked, plus the Facebook Messenger app. Lots of other messaging and chat apps have also been banned including WhatsApp and Viber. The justification is that they are being used to organise criminal behaviour, although no more details seem to be available. The idea is a long standing one, if your population are organising protests, strikes and rallies then block as many social networking sites as possible.
Obviously these inept measures have been matched with a similar hapless technical implementation, with a combination of different methods used depending on which ISP you choose. The reality is that it's a very haphazard ban and one that's very easy to bypass by using a VPN or proxy. In fact thousands of people already use these to watch the BBC abroad and will similarly be unaffected by the blocks in any case.
As a method of blocking civil disobedience and political dissent, it's a hopeless and desperate move. It has much the same same (non)-effect as Turkey who frequently use this method with negligible results other than to earn the derision from the population and civil rights organisations across the world. Bangladesh seem intent on dealing with their problems by picking an easy and inneffective target - social media.
Incidentally if you're in Bangladesh and affected by this block, please read my post here - http://www.anonymous-proxies.org/2009/04/facebook-banned-facebook-blocked.html which shows you how to use the demo version of Identity Cloaker to bypass blocks to Facebook. It's 6 years old but still works although the demo version won't help with the other social applications that are being blocked.