In Anglo-Saxon England, the bounty for killing an outlaw was the same as for killing a wolf. By the late Middle Ages, this had evolved into the legal principle of wolfesheed: the outlaw was a wolf, able to be hunted and killed exactly like a wolf, legally and by any means. England wasn't the only place that so closely equated wolves with criminals: in the Norse sagas, murderers are Ulfr or wear wolf cloaks.

Although it is fairly common for cultures to equate criminals with dangerous animals, the link in medieval Europe between bandits and a type of animal particularly known for attacking travelers and traveling in packs is both strong and specific. Travel in the Middle Ages was dangerous business, and it wasn't just a case of humans versus animals and environment.

Overland medieval travelers faced several varieties of human threat. First--you might have noticed that university diplomas grant the holder the rights and privileges associated with the degree. Well, those rights and privileges originated in the Middle Ages, and the very first one--from twelfth century Germany, even before universities existed as such--was safe conduct for students and teachers traveling between schools or between home and school. The retinue of a lord whose land they were passing through, or a band from a city, had a very very nonzero chance of kidnapping travelers for ransom--whether they could come up with the money on their own, or whether a messenger had to be sent back to their family. (The struggle to reign in robber knights and lords is an important part of the medieval political narrative--it was a slow and very hard-fought process). Timothy Reuter posits that noble/aristocratic robbers (including those more or less employed by them) were actually the primary danger in the Middle Ages versus "career bandits."

It wasn't just people and their ransom that roadside robbers would be after. When attacking merchants' caravans, wine was a popular theft item--also copper, iron, cloth, basically anything that could be sold. Remember, in many or most cases, we're dealing with people well integrated into the socio-economic fabric of medieval society. This would in many cases continue to apply to the next grouping I'll discuss.

There were also robbers and kidnappers from lower social classes who acted like they were legitimate groups or armies. In general, this type of banditry would rise out of a broader conflict or war, like a massive heterodox movement/suppression. The best example here is probably the bratczycy or "brothers" in fifteenth-century Hungary. They seem to have the veneer of--and claimed to be--Hussite armies but in reality were pretty much gangs of bandits. The wartime context of groups like these is key. Medieval banditry--murder, plunder, robbery, arson, rape--looked pretty much like what the average soldier did during war. More to the point, what the average soldier was expected to do and what was societally accepted as "what soldiers did." While making little difference to travelers, the attempt for a group to portray themselves as legitimate soldiers at war could matter for their own legal circumstances if caught.

And then, of course, there were indeed archetypal bandit gangs of vagabonds--maybe already outlaws where such a status existed. Feodor Glowaty's family/gang at the end of the 15C Poland lasted longer than most (about three years), so it's a good example of the sort of "career bandit" life as opposed to a one-time robbery or a landed robber-knight. Glowaty's group, which had about twenty members at its height, became most infamous for a massive robbery of the Rozgonyi estate, including making off with a large number of horses. They also engaged in attacks on merchant caravans and locals moving between village to village. And most famously, in 1493, they held an entire town for ransom as punishment for capturing and executing two of their members. Well, they tried to, at least. It's pretty clear the town didn't pay.

It's tempting to say that over the course of the Middle Ages, the proportion of aristocrat/servant-robbers declined and the proportion of vagabond and/or outlaw and/or desperate robbers increased. Civic criminal records show that many thieves operated on a bare survival level rather than bigger heists, and it seems reasonable that their counterparts outside the town walls might have been in similarly desperate circumstances. The agonizing long-term reigning in of wayward lords, on the other hand, operated at different speeds and scales in different parts of Europe. And as the case of soldiers/claimed soldiers demonstrates, it's not a matter of "noble OR outlaw," but a sliding scale that likes to tip up and down at different times.

As far as protection, the most important thing to remember is that attack was by no means a guarantee. Travel increased exponentially over the course of the Middle Ages--both local and long distance. In other words--most of the time, it was successful, and that most of the time was enough to be worth the risk. That said, there were a couple of basic ways travelers could protect themselves. The first is probably the most obvious: travel in groups. When Ibn Battuta crossed North Africa on his way to Mecca, he was basically told, "Nope, you're waiting until the caravan goes this year, full stop."

It's also evident that travelers, perhaps especially merchant groups with valuable cargo, were often armed. Even at the sporadic times and places where weapon-carrying was regulated in medieval Europe, exceptions were frequently made for travelers.

Escorts are a trickier business to suss out of the sources. There are a few references to a ruler decreeing a soldier would accompany caravans between towns (especially in Italy), but in practice, this seems to have worked out symbolically far more than actually--almost a means of insurance, if cargo was stolen the merchant might be reimbursed for part of it. Italian bankers paid handsomely for military protection of their largest transports, especially if straight-up currency was involved.

Disguise was another popular method of attempted protection. By the late Middle Ages, pilgrims in medieval Europe had a distinctively coded style of dress. It might sound silly, but in fact, there are comparably few reports in sources of pilgrims being attacked--and a whole lot of complaining about not-pilgrims using pilgrim attire to conduct espionage, moneymaking business, or simply avoid payment of tolls at bridges and towns.

And, indeed, the final method of protection wasn't really protection at all. Jewish and Christian sources alike debate whether it is moral to just go ahead and buy back your stolen merchandise from the thieves.

Overall, highway banditry was indeed a problem in the Middle Ages, particularly in the more lucrative high-traffic areas between nearby towns or around a city. The most risk, indeed, was carried not by long-distance travelers but by everyday business. And while homicides and robberies flare up in legal sources, a lot of bandit activity would basically have consisted of bribes or "paying for safe passage, wink wink." Scholars have also suggested that roadside crime increased over the course of the Middle Ages--laws against banditry become more common proportionally; inns and hostels spring up on the roadside to accommodate/protect travelers overnight. But this only makes sense. More people traveling more often and with more money--and more to the point, more reasons to have money.

A similar question was answered by /u/NewYorkeroutoftown in this thread:

https://www.reddit.com/r/AskHistorians/comments/55pdq9/how_prevalent_was_the_threat_of_bandits_in/

Here's a very similar thread from (2014)[https://www.reddit.com/r/AskHistorians/comments/2mx20x/works_of_medieval_fantasy_often_depict_bandits_or/].

It may have been a problem all over, not just Europe. I will need someone to verify this, but I remember something about Buddhist temples being placed along the Silk Road. They were used like outposts and banks, like a safe haven for travelers. The monks learned martial arts to fend off bandits while traveling and also to protect the temples.

My question is if Europe had a similar banking system, or route set up that had to be protected in a similar way?

In what is today known as Switzerland, exile was a pretty common form of punishment (Historical encyclopedia of Switzerland. Available in german, french and italian. Check on the upper right to change the language): Exile is simple, doesn't cost anything and the criminal is out of town: Problem solved, right? All these petty criminals were doomed to live a life in the woods with no possibility to earn money and without access to any markets. In their miserable situation they started to mug travellers. At the beginning alone or with a companion, and soon enough, they attacked in what we would describe as gangs (Historical encyclopedia of Switzerland. As the encyclopedia elaborates, these gangs operated in lose formations and with a wide network of fences covering big parts of Switzerland and neighbouring territories. This problem enhanced when unemployed swiss mercenaries returned and financed their life by robbing travellers. At peaks 40% of the homeless criminals are believed to have been mercenaries. At the same time something like a police force didn't exist. Towns with 2000 citizens had one nightwatchman, nothing else. Whenever someone needed help, the nearest town had to organize a few voluntary horsemen to engage. Needless to say, they usually arrived too late at the scene. So as long as no one sent soldiers or mercenaries to secure particular routes, just leaving town or a village was extremely dangerous.

Edit: Added first two sources and details about the criminals and their background.

I would love to read an answer to this question but regarding China. Learning about people like Li Zicheng, who raised an army of 'bandits' and overthrew the Ming dynasty, is always fun.

This relates to a later period (17th c and onward), but a fun reference you might enjoy is the Old Bailey online--you can look up actual cases of highway robbery, read case overviews, see verdicts, etc. Here's a link.

Were the bandits violent?