A computer hacker has attempted to poison a city’s water supply with a caustic chemical.
The hacker, who breached the system at the city of Oldsmar's water treatment plant in Florida on Friday (local time) using a remote access program shared by plant workers, briefly increased the amount of sodium hydroxide by a factor of one hundred - from 100 parts per million to 11,100 parts per million, Pinellas County Sheriff Bob Gualtieri said.
Sodium hydroxide, also called lye, is used to treat water acidity but the compound is also found in cleaning supplies such as soaps and drain cleaners.
It can cause irritation, burns and other complications in larger quantities.
A plant worker first noticed the unusual activity about 8am on Friday when someone briefly accessed the system but thought little of it because co-workers regularly accessed the system remotely, Sheriff Gualtieri said.
But at 1.30pm, someone accessed it again, took control of the mouse, directed it to the software that controls water treatment and increased the amount of sodium hydroxide.
The sheriff said the intruder was active for three to five minutes.
When they exited, the plant operator immediately restored the proper chemical mix, he said.
Other safeguards in place - including manual monitoring - likely would have caught the change in the 24 to 36 hours it took before it reached the water supply, the sheriff said.
Sheriff Gualtieri said the public was never in danger.
But he did say the intruder took "the sodium hydroxide up to dangerous levels".
Oldsmar officials have since disabled the remote-access system and say other safeguards were in place to prevent the increased chemical from getting into the water.
Investigators said it wasn't immediately clear where the attack came from - whether the hacker was domestic or foreign.
The city has a population of 15,000.
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