The word, malin(hear), has a negative connotation. According to the dictionary it means shrewd or cunning. In fact, the phrase malin plaisir(hear) means malicious pleasure, and attributed to devil himself.
I am sure you must have figured this out even without my referring to the dictionary because of the use of the prefix ‘mal’. This is true not only in English but also in French: malheureusement (hear) is opposite of heureusement (hear)and means unfortunately.
It therefore took me a while and a little help from Google Translate to understand what the following meant: Une carte pour voyager malin. (hear une, carte, pour, voyager)
It certainly could not be a malicious travel card. Turns out that it means ‘a smart card for travel’.
I guess that there is a very thin line between being smart and being cunning. And to be smart one needs to be cunning too.