There's no shortage of online platforms that allow consumers to post reviews of businesses, products and services -- but before you post it's important to understand the possible legal repercussions.

U.S. cybercrime and privacy lawyer Parry Aftab says that while many users often think the anonymity of posting something on the Internet grants them a certain degree of immunity, that's not really the case.

"Defamation exists online and offline, and if you cross that line a lawyer is going to send you a letter and you're going to have to face the music," she told CTV's Canada AM.

But Aftab said that if the review is true then it doesn't necessarily have to come down.

"If you're posting something honestly and in good faith, a lawyer's letter is not going to make a difference, because truth is an absolute defence to defamation," she said.

However, if the review is untrue, then you may face court or be asked to delete the review to avoid going to court, she added.

Aftab noted that these guidelines apply across the board, to both business owners and consumers alike.

A 2012 Ottawa case made international headlines after a restaurant owner was sentenced to 90 days in jail, after she was found guilty of libelling a customer who gave her restaurant a bad review online.

In that case, the restaurant owner responded to the review by revealing the customer's full name and giving out her phone number and other personal details. The owner later pretended to be the customer, sending sexually explicit emails to her boss.

"When you cross that line and you use digital technology as a weapon, you have to recognize that you may (face) consequences," Aftab said, noting that it's similar to cyberbullying.

She added that there have even been some cases where competitive restaurant owners have pretended to be customers who had problems at other eating establishments, just so they could post negative reviews.

Aftab said the best thing to do when you want to post a negative review is to give yourself a "cooling off" period and post it later.

"That way you're not in a raging fury and doing things that alcohol might help you do… and what you post tomorrow will be helpful to others and to you as well," she said.