Ronald Kessler, a former Washington Post and Wall Street Journal investigative reporter, is the New York Times bestselling author of 'The Trump White House: Changing the Rules of the Game' and 'In the Presidents Secret Service: Behind the Scenes With Agents in the Line of Fire and the Presidents They Protect.'

The Secret Service has substantially toughened security at Donald Trump's Mar-a-Lago resort after three potentially harmful intrusions and now as Iran has put out an $80million hit on the president.

No longer can anyone wander onto the Palm Beach property under false pretenses, as happened last March with Yujing Zhang from China.

Depending on where members and guests are headed on the property, they now may have to pass through as many as four Secret Service security checkpoints.

Their identities are checked based on their driver's licenses, and their vehicles are examined for explosives under the hood and in the trunk. They must pass through metal detectors or be wanded for weapons or explosives at several more check points.

The added security should make it impossible for intruders to sneak in again, avoiding repeat incidents by trespassers Mark Lindblom, a college freshman who wandered around the resort for 20 minutes during Trump's 2018 Thanksgiving visit and Chinese national Jing Lu, who entered the grounds last month to try to take photos without being immediately apprehended by Secret Service agents.

Secret Service has ramped up security at Trump's Mar-a-Lago resort in Florida as recent as his last visit where Secret Service members are seen behind the president as he boards Marine One

The beefed up security came after Hesameddin Ashena (left) dropped a chilling hint of an Iranian attack on Donald Trump 's property empire after the death of military commander Qassem Soleimani (right)

Members and guests must pass through as many as four Secret Service checkpoints and their vehicles examined for explosives under the hood

Now the presence of Secret Service agents and uniformed officers appears to have been increased by at least a third.

Ramped up Secret Service security has also been imposed at Trump International Golf Course in West Palm Beach, where President Trump goes to play golf or partake in buffet dinners.

Under the new protocol, identities of club members and guests are checked with their driver's licenses, and vehicles entering the property are examined for explosives under the hood and in the trunk.

Ronald Kessler, pictured above with Trump, is also a former Washington Post and Wall Street Journal investigative reporter

The tougher measures by the Secret Service are in addition to protection by the Air Force, which enforces a no-fly zone over Mar-a-Lago when Trump is in town, the Coast Guard, which patrols the waters around Mar-a-Lago, and Palm Beach and Palm Beach County police, who shut down roads leading to the former Marjorie Merriweather Post estate and inspect trucks approaching the area when Trump is in town.

The U.S. Army also maintains a contingent on the grounds in case needed.

Troubling as the recent intrusions at Mar-a-Lago were, they were trivial compared with the repeated Secret Service fiascoes that took place during the Obama administration.

Back then, Michaele and Tareq Salahi went prancing into a White House State Dinner and were greeted by President Obama even though they were not on the guest list.

In a story I broke, Secret Service agents were hiring prostitutes when Obama visited Cartagena, Colombia. Back home, inebriated Secret Service agents drove their car up to the White House itself and interrupted an active bomb investigation. And intruder Omar J. Gonzalez jumped the White House fence, ran into an unlocked White House, and entered the East Room armed with a folding knife.

Underscoring the agency's arrogance and cover-up tendencies, then Secret Service Director Julia Pierson publicly claimed that in not killing Gonzalez, Secret Service uniformed officers exercised 'tremendous restraint.'

Pierson coupled that with false statements she approved saying that Gonzales had been quickly detained at the door and a search determined that he was unarmed. Pierson later admitted at a House Oversight and Government Reform Committee hearing that she knew that Gonzalez in fact carried a weapon when he was arrested.

Senior FBI officials were horrified by the Secret Service's handling of the matter and found laughable its effort to cover up its own failure by brazenly hailing the officers' 'restraint.'

Just after Trump became president and before he had appointed his own Secret Service director, Tuan Anh Tran jumped the fence carrying two cans of pepper spray. He advanced along the exterior of the White House as far as the entrance to the Diplomatic Reception Room.

In the firing line? Donald Trump's resort at Mar-a-Lago, Florida (pictured), where he was holidaying when he ordered the hit against Soleimani

Chinese nationals Yujing Zhang and Jing Lu were both detained after trespassing on Trump's Mar-A-Lago property on two different occasions

Mark Lindblom, a college freshman, trespassed and was detained by Secret Service members while Trump was celebrating Thanksgiving in 2018

A Secret Service report that I obtained under the Freedom of Information Act concluded that during the 17 minutes Tran was wandering around White House grounds just before midnight on March 10, 2017, Secret Service uniformed officers repeatedly ignored or dismissed the alarms he triggered until he was finally arrested.

Rather than respond to the alarms, officers reported that they could not see anyone or that the intruder looked like he might be a member of the White House staff or a uniformed officer.

Under Secret Service directors appointed by Trump, while people have jumped the fence, no one has been able to get near the White House itself, much less enter it.

Secret Service agents tell me that reforms instituted by Trump's Secret Service directors, Randolph D. Alles, a former Marine, and current director James M. Murray, a former assistant USSS director, are responsible for the agency's turnaround.

The stepped-up security at Mar-a-Lago that began with the president's Christmas and New Year's Eve visit is another sign that the Secret Service has reversed its downward plunge that began under Obama.

Trump is suitably grateful. At the Trump International Golf Club in West Palm Beach just before New Year's Eve, Trump friend and Mar-a-Lago member Gary J. Giulietti, who as president of Lockton Cos. is a consultant to Trump on insurance issues, noticed that Trump invited his agents and the agents guarding his family members to help themselves to the spectacular Sunday evening buffet.

Thousands of people gathered in Tehran for the second day of Qassem Soleimani's funeral after he was killed in a US drone strike ordered by Trump on Friday

Besides prime New York strip steaks grilled to order, they feasted on lobster Newburgh, freshly shucked oysters on the half shell, huge cocktail shrimp, stone crab claws, sushi, braised scallops, deep fried soft shell crabs, seafood paella, rack of lamb, prime rib, pork roast, cakes and pies, and make-your-own hot fudge sundaes with choice of dark chocolate or milk chocolate sauce.

'He was feeding all the agents, who were completely blown away,' Giulietti told me.

In contrast, Hillary Clinton is so nasty on a daily basis to her agents, who still protect her, that being assigned to her detail is considered a form of punishment and the worst assignment in the Secret Service.

Sitting on a couch overlooking the main Mar-a-Lago pool, I once asked Trump how he likes being protected by the Secret Service.

'It's great,' he said. 'I have agents all around me as I'm playing golf, and they are all looking in different directions, so when I miss a shot, they don't see it!'