Memorial Day is one of the most important holidays in the US. Thousands of military parades take place as millions of people pay their respects to the country’s fallen soldiers. Security services are on high alert as the day gives terrorists the perfect opportunity to strike at the very heart of the superpower. Back in 2013, it seemed like everyone’s worst fears had been realised.

Sleeper cells had seemingly carried out perfectly coordinated attacks: in four US states, explosions occurred at critical junctures on the electrical grid. Tens of thousands of people were affected, stuck in lifts or traffic jams. Rumours of a large-scale hacker attack quickly spread. Who was behind it? Were the Russians to blame? The Chinese? Actually, the truth is somewhat more prosaic. The perpetrators were homegrown. What’s more, they used neither computers nor explosives to carry out the attack – their weapons were their own four paws…

HOW DOES A RODENT TURN OFF THE ELECTRICITY? – Critical infrastructure – power grids, communication networks and traffic systems – forms the backbone of society. Tamper with them and civic order quickly breaks down. For years, intelligence services have discussed possible ways in which hackers could bring a country to its knees.

Governments allocate more and more resources to combat this supposed danger: “We face a cyber Pearl Harbor, a new 9/11,” warned then-US Secretary of Defence Leon Panetta in 2012. “The greatest risk is a catastrophic attack on the energy infrastructure,” General Keith Alexander, chief of the United States Cyber Command continued. “We are not prepared for that.”

What’s happened since then? Nothing. Or rather, the enemy is of a completely different kind. You see, it’s not people behind the attacks, but curious animals: birds, jellyfish, ants and, above all, squirrels. Strictly speaking, the latter are the true architects of cyber-terrorism. In some US states, every second power outage caused by an animal is down to the bushy-tailed beasts.

They were also the culprits on Memorial Day, 2013. In contrast, there have only ever been three or four proven successful attacks on industrial installations by hackers using the internet. The reason? “That kind of cyber attack is very difficult,” explains IT security expert Bruce Schneier. There’s a huge amount of programming and expenditure involved in creating a virus, which only well-equipped and well-funded secret services can afford. And even then, it takes months or years to plan.