Mallus (malwari, malbari) are used in a form of abusive word. They are every where in UAE - clerks, accountant, teachers, manager, business tycoons, restaurants (south Indians, people from Kerala, language = malyalum). But also people from Madras, who speak madrasi, & who speak tamil, are mistaken of Mallus. You can see them with colorful shirts & Lungi 
Majority I think they are popular because of their eating habits (they carry their food everywhere they go & it smells) this oil on their head (which stinks) and the color combination they do (red with yellow and Gold) so whenever we do something outa fashion, our friends shout out “How Malluishi”.
This word is equivalent to Paindo which we use in Pakistan.