How do wizards prevent Accio-fueled robberies?

Question

It looks like from canon examples, Accio works on:

• Summoning things that aren't yours (Hermione summoning books about Horcruxes that Dumbledore took out of the library in DH)

  "Well... it was easy," said Hermione in a small voice. "I just did a Summoning Charm. You know – Accio. And – they zoomed out of Dumbledore's study window right into the girls' dormitory."

• Summoning things you aren't sure of their exact location (Molly summoning twins' toffees in GoF):

  'Accio! Accio! Accio!' she shouted, and toffees zoomed from all sorts of unlikely places, including the lining of George's jacket and the turn-ups of Fred's jeans.

• Summoning things that are "nailed down" (Twins summoning their brooms before escaping Hogwarts in OotP)

  And before Umbridge could say a word, they raised their wands and said together:
  'Accio brooms!'
  Harry heard a loud crash somewhere in the distance. Looking to his left, he ducked just in time. Fred and George's broomsticks, one still trailing the heavy chain and iron peg with which Umbridge had fastened them to the wall, were hurtling along the corridor towards their owners; they turned left, streaked down the stairs and stopped sharply in front of the twins, the chain clattering loudly on the flagged stone floor.

• Summining things from a fairly big distance (Harry summoning his Broom to the TriWizard tournament's first task from the castle).

As such, is there any canon explanation for why people like Mundungus (or Tom Riddle) who have very little respect for the law or private property don't simply Accio whatevertheheck they want to steal out of people's homes?

Answer 1

We know that charms exist to prevent the use of summoning charms to steal objects. For example, in Deathly Hallows, when the trio are searching for the locket in Grimmauld Place:

“There’s an easier way,” said Hermione, as Harry wiped his inky fingers on his jeans. She raised her wand and said, “Accio Locket!”

Nothing happened. Ron, who had been searching the folds of the faded curtains, looked disappointed.

“Is that it, then? It’s not here?”

“Oh, it could still be here, but under counter-enchantments,” said Hermione. “Charms to prevent it being summoned magically, you know.”

“Like Voldemort put on the stone basin in the cave,” said Harry, remembering how he had been unable to Summon the fake locket.

Although the summoning charm fails because the locket isn’t actually there, Hermione makes it clear that such counter-measures exist, and that it’s plausible the Blacks would be using them.

This is hinted at again when they’re raiding the Lestrange vault:

“Accio Cup!” cried Hermione, who had evidently forgotten in her desperation what Griphook had told them during their planning sessions.

“No use, no use!” snarled the goblin.

Both Gringotts and Grimmauld Place have stringent security measures; you’d expect them to have anti-summoning charms at the very least.

In The Book of Spells¹, this concern is addressed directly in the entry on the summoning charm:

Most magical objects are now sold carrying anti-theft devices that will prevent them being Summoned by any but their owner.

This would prevent somebody summoning items directly from somebody’s home, if the item was purchased from a magical shop. This doesn’t address how to protect items obtained from Muggle shops, or ones that you made yourself (such as Fred and George’s toffees). However, I think this probably makes life difficult enough for thieves that they’d pursue other methods.

The same entry includes a story of the Accionites, a group of wizards who stole everything by summoning. As suggested in the comments on the question, this attracted a lot of attention when they tried to steal some goblin weaponry. The goblins were not best pleased.

^{1 I haven’t seen this used as a source on many parts of the site, but it’s listed on JKR’s site as affiliated with Pottermore, so I think I can quote it as canon.}

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Addendum

The two supplementary textbooks (Quidditch through the Ages and Fantastic Beasts and Where to Find Them) give us a name for at least one of these counter-enchantments: the Thief’s Curse.

Quidditch:

By buying this book – and I would advise you to buy it, because if you read it toolong without handing over money you will find yourself the object of a Thief's Curse – you too will be contributing to this magical mission.

Beasts:

All that remains is for me to warn anyone who has read this far without purchasing this book that it carries a Thief’s Curse.

In neither book does Dumbledore go into any detail about what this curse entails, but the phrasing suggests that its effects would be well known, and unpleasant.

Answer 2

When Hermione taught Harry how to use accio in book 4, we learned that accio could only be activated when the spell caster already know the object,

Example: If the thief only wanted to summon some galleons:

In mid day, accio could be countered with protego by anyone in the house as they saw things moving out to the robbers, just like what harry did in book 7,

However, while everyone is asleep at mid night, I could only imagine they use the same charm as in Gringotts, Voldemort's cave, and again in book 7, to protect against accio, if they did, it would work in mid day too, so its useless even just to try it.

The problem is, that if they want something far more precious than just some galleons, then it would be hard just to know what the object is like, as Harry needed more than half the book just to know what Ravenclaw's diadem looks like, and usually these treasures would be protected by any charm not to mention the anti-accio charm, like what hockey was instructed to do by Hepzibah Smith, to save the Slytherin's and Hufflepuff's away with the usual charm's.