Cash is out. Mobile payment apps are in. You know this already because you use Venmo for everything from drinks with friends to utilities with roommates to passive aggressive charges with enemies. We all know the many practical uses of mobile apps, but less well-known are the mobile app horror stories told by Millennials around the Netflix campfire.

“Someone just tried to hack my Instagram account from India, and now I can’t log back in because I don’t know my password.”

“I gave a guy my phone at the bar because he wanted to give me his number, and he Venmo’d himself from my account.”

“After I passed out in the backseat the Uber drove around for an hour. I got charged $90 to go two miles.”

When bartering in the Cloud things can get dicey. With this in mind I came up with some tips to help eliminate surprises in your personal mobile economy.

Mobile apps have revolutionized our personal finances. Spending money on the Internet is simpler than carrying cash or writing checks. That’s why I know so many people who have their credit card information memorized for online shopping. However, with increased accessibility come increased security risks, some of which might not be so obvious to casual users.

The beauty of Venmo is seemingly instant transactions. You’re short on cash, you forgot your wallet, or the server won’t split the check. So, you Venmo your friend a sushi emoji with the agreed upon amount, and the friend’s Venmo balance reflects the exchange of money immediately. Venmo exists for easy and quick payments such as this.

But in reality, money is not transferred immediately. Funds won’t be transferred between accounts for at least a full business day. Scammers have taken advantage of Venmo users who aren’t aware of this system. In the period of time that the transaction takes to process, one user can cancel the transaction.

To put it in perspective, when you decide to sell your Coachella ticket because you don’t want to watch Beyoncé give birth on stage make sure you let the Venmo charge sit for a day before you send the tickets. If you send the tickets too soon the buyer could cancel the charge. The fake buyer gets the tickets, and you don’t get paid. According to Slate, hundreds of thousands of dollars have been stolen on Venmo in this fashion. Beware of strangers who insist on using Venmo.

Business transactions on Venmo, in general, are probably a bad idea. Especially because if you get ripped off Venmo won’t back you up. Their user agreement states, “Business, commercial, or merchant transactions may not be conducted using personal accounts.”

The best way to not get scammed is to secure your apps. Mobile apps are constantly taking steps to improve authentication of transactions. Venmo sends an email notification when there’s activity on your account. Twitter and Instagram send notifications when you log in on a new device. Pay attention to these notifications, even if it’s just a glance. However, leaving the security of your finances to apps themselves would be unwise. You should take steps to secure your apps before a problem occurs.

If your phone gets stolen your pass code on the lock screen is not enough to keep your apps safe (see wikiHow article entitled “How to Hack an iPhone’s Pass Code (with Pictures)”). Venmo has a security feature that requires a fingerprint or pass code every time the app is opened. Extra security won’t garuantee the safety of your money, but it could slow down a hacker long enough to allow you to cancel your Venmo account or credit card.

For more Venmo related fun, check out a website called Vicemo which collects all public transactions related to drugs, booze, and sex.