Publication | Legaltech News

Nervous System: Cybersecurity 1800s Style

David Kalat

May 8, 2024

Hacking may seem like a current phenomenon, but in the 1830s, a pair of brothers managed to carry on a scheme of hijacking the French national telecommunications network for two years before being caught.


In the contemporary world, some traders take advantage of timing differences as small as fractions of a second to gain a competitive edge over others. Nearly two hundred years ago, those timing differences were measured very differently. Back in 1834, information about market developments traveled slowly. Traders in Bordeaux, for example, had to wait days for up-to-date information to be delivered from Paris by stagecoach. One could transmit data swiftly across great distances using telegraph networks, but those were limited to governmental use—that is, until a pair of clever hackers figured out how to exploit that early data network for their own fraudulent gain.

Since 1794, the French national telecommunications network had been an optical telegraph system based on semaphores. To transmit a message across the country, an operator at the origin end would use ropes and pulleys to position large wooden beams on the top of a high tower. The position of each beam would indicate a specific character in the message to be sent, character by character. Towers were situated at intervals of roughly 8 to 10 kilometers, allowing operators along the chain to update their own semaphore arms’ positions to match those of the originating transmitter. As each tower in sequence would see the previous tower’s signal positions, and update its own flags accordingly, the message moved down the line.

One consequence of this design was that errors tended to propagate down the chain. If an operator positioned an arm incorrectly, the next tower operator was likely to match their flags before the mistake could be corrected. To account for this, the system incorporated a retrospective error-correcting mechanism. If an incorrect character was transmitted, the operator would immediately follow it with the equivalent of an “oops” character directing the recipient to ignore it.

As it happened, the mistake character and its backspace correction would be faithfully transmitted through every intermediate station and only acted on when the message was ultimately transcribed at the final destination.

Twins Joseph and François Blanc realized that if someone intentionally inserted an extra character into a message along with the correction character, that extra character could piggyback on an official message without anyone noticing. The official message would eventually be decoded intact and unaltered, leaving no trace of the hijack.

To make the scheme work, the Blancs needed a team of confederates: first, someone inside the Paris stock exchange to look out for important trends in the bond market; then corrupt telegraph operators willing to secretly insert intentional “errors” into official messages; and last, someone near the Bordeaux telegraph station to watch for any passing transmission “errors” to be noted and relayed to the brothers.

When bond trading swung enough points in one direction or another to warrant a message to the Blancs, the Paris accomplice mailed a package of sample clothing items to one of the telegraph operators in Tours who had accepted the bribe. The clothing item in the package, such as socks or neckties, along with the color of the item indicated the extra character the operator should insert and then immediately cancel out.

In exchange for their participation, the Tours operators were paid 1500 francs upfront, followed by a monthly stipend of 150 francs every month, and an additional 20 francs for each hacked message. At the time, an ordinary telegraph operator took home a daily wage of less than 2 francs.

The brothers kept their gimmick going for two years, transmitting over 120 messages before anyone noticed. The plan could well have continued indefinitely if not for the vicissitudes of fate. Eventually, one of the bribed operators in Tours fell ill and had to miss work. Not wanting to lose out on the gravy train of the Blanc’s payments, he explained the situation to a colleague in the hopes the other fellow would substitute for him while he recovered. That other operator had a different moral compass and turned the matter over to the police.

The Blancs were put on trial in 1837, but the authorities struggled to establish exactly which law they had allegedly broken. The law had not kept up with the state of technology, and while what the brothers did was certainly dishonest, the law had not expressly forbidden the use of the telegraph system in this way. The Blancs were made to pay a fine for bribing public officials and were let go. A new law was hastily drafted in the immediate aftermath of the trial to address future incidents of a similar nature.


The views and opinions expressed in this article are those of the author and do not necessarily reflect the opinions, position, or policy of Berkeley Research Group, LLC or its other employees and affiliates.

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David Kalat