Sylvester Stallone is alive.

The actor and his brother took to social media on Monday to reassure the world of this fact after a hoax began circulating on Facebook and Twitter that claimed the actor had died at the age of 71 following a battle with prostate cancer.

The hoax, the origin of which is unclear, was fairly transparent - Stallone has been steadily working, recently appearing in an episode of "This Is Us" and filming several movies, according to IMDb.

Perhaps that's why he seemed to brush it off in an Instagram post.

"Please ignore this stupidity," he wrote in the post, "Alive and well and happy and healthy."

"Still punching!" he added, referring to his most famous character, the boxer Rocky Balboa.

His younger brother, musician Frank Stallone, had far harsher words for whoever started the hoax.

"Rumors that my brother is dead are false. What kind of sick demented cruel mind thinks of things like this to post? People like this are mentally deranged and don't deserve a place in society," he wrote on Twitter, adding, "I'm very protective of my older brother and I don't find any humor in this fake post today on my brothers demise. It upset my 96 yr old mother so I'm doubly upset. I just can't understand what makes these sick minded people tick?"

This marks at least the second time that false rumors of Stallone's death circulated online. The first time, in September 2016, a fake CNN report of his supposed "death" appeared on Twitter, as NME reported at the time.

That shouldn't be too surprising. The actor is far from the first person to be a victim of a celebrity death hoax. They've been around for ages. In 1966, a small swath of rock fans claimed Paul McCartney died and was replaced by a look-alike.

The rise of social media has made the spreading of such rumors easier. It's become a common internet prank. Among the celebrity targets of an online death hoax: Betty White, Jack Black, Robert Redford, Macaulay Culkin, Queen Elizabeth II and Jackie Chan, and that's just the tip of the iceberg.

In 2010, a Twitter user with fewer than 1,500 followers tweeted that CNN reported Morgan Freeman had died in his Burbank home, according to Slate. The story swept across the internet, eventually prompting CNN to set the record straight.

The Twitter user later said, "It was an inside joke between friends. I had no intention of things turning out this way."

One reason hoaxes spread, even from such a minor Twitter account, is because people care about celebrities, according to BuzzFeed media editor Craig Silverman.

"Fake news relies on viral sharing," Silverman told Digiday. "If you think about why so many stars are subject to death hoaxes, they've been part of a pop culture that people have an emotional connection to. And that is at the core of what makes fake news work."

Mark Bell, an Indiana University adjunct professor who focuses on deception in digital media, said many hoaxers find deception exciting.

"People like to lie," Bell told the New York Times in 2012. "They get a thrill from it. There is a little hit of dopamine when you lie, especially a lie that is believed by somebody else."

Some hoaxes are phishing scams, such as the story claiming Brad Pitt had killed himself that began circulating on Facebook in 2016. The post was mocked up to look like a Fox News report, complete with the network's logo and the tag line, "A purported FOX NEWS Video showed that the Hollywood actor hanged himself."

Users who clicked on the post were not redirected to the Fox News website but a random page that requested their log-in information, which would allow hackers to access their personal data, as CBS News reported at the time.

Meanwhile, some fake news websites that, at first glance, appear to be legitimate, such as "MSMBC" and "Usmagazine.us," get advertising revenue for every click. They use celebrity hoaxes on social media to receive a windfall of clicks and money, as The Washington Post's Jessica Contrera reported in 2016.

Most hoaxes can be avoided with a few internet searches and a sharp eye. The Post's Caitlin Dewey compiled seven simple steps to spot a hoax, which include looking for a byline on the story, verifying the source of the news and keeping an eye out for proper grammar and punctuation.

It's useful information because, as sure as Sylvester Stallone is still alive, another celebrity death hoax is right around the corner.