Discoloured bricks

[tottenham1]

Some of the brick work on a house I am looking to purchase has black coloured markings on it, it looks like spots of mould but is dry to the touch. The brick work is slightly pitted in some areas around this. Do you know what this is how can it be remedied?

The house is an end terraced, about 5 years old and the other houses have a similar problem.

Thanks for your help

Regards

Matt