The Barbadian songstress' rumored boyfriend Matt Kemp and her friends are all worried about the issue, suggesting her to hire extra guards.
Rihanna has reportedly stepped up her security after a male fan allegedly sent her saucy letters. The "Umbrella" hitmaker is said to have been the target of X-rated messages in the post from one mystery man.
And her rumored boyfriend - baseball player Matt Kemp - is so worried about the situation, he's advised the singer to be wary of any mail she receives, according to Britain's Daily Star. A source tells the publication, "Matt has asked Rihanna's team to be extra cautious since she was sent two very steamy letters."
"Her friends are also concerned about the situation. They spent ages talking about it when they dined at the Spanish Kitchen in West Hollywood last week. They are really worried things with this guy are going to get out of hand."