RYE BROOK, N.Y. — The United States has many colossal dams, hydroelectric[1] power generators like Hoover and Grand Coulee so monumental in scale and purpose that they have been celebrated in song by Woody Guthrie and others.

The Bowman Avenue Dam in this low-key suburban village in Westchester County is not one of those. Its opening is about the width of a modest living room, and the 20-foot-tall dam itself essentially keeps a babbling creek, the Blind Brook, from flooding basements and ground floors in houses downstream.

Yet, according to the authorities, it was the computer-guided controls of this dam that seven Iranian computer hackers chose to penetrate on behalf of that country's Revolutionary Guards Corps[2], as part of a plot[3] that also breached or paralyzed 46 of the nation's largest financial institutions and blocked hundreds of thousands of cu stomers from accessing their bank accounts online. The cyberattacks were disclosed in an indictment[4] that Attorney General Loretta E. Lynch announced on Thursday.

"It's ridiculous how little that dam is, how insignificant in the grand scheme of things," said Paul Rosenberg, the village's mayor. "We're not talking about something vital to the infrastructure of the country."

Map | Rye Brook map

The mayor, despite being puzzled by Rye Brook's role in the alleged plot, had several theories about why the village's sluice-gate dam had been singled out. One was that the Iranian hackers had confused the structure with another named Bowman — the Arthur R. Bowman Dam on the Crooked River in Oregon, which is 245 feet tall and 800 feet long, and is used to irrigate a large swath of local farms.

Mayor Rosenberg also speculated that the hackers had gone after the Rye Brook dam in a dry run for a more disruptive invasion of, say, a major hydroelectric generator or some other grand and indispensable element of the nation's power grid.

Any attempt to remotely manipulate the Bowman Avenue dam would have failed because it was under repair and offline at the time that the authorities say the Iranians were trying to take it over. American investigators were nevertheless disturbed because the attempt indicated that hackers could take control of computer-operated infrastructure.

Despite being unsung, the dam — which is less than 15 miles north of the Bronx and is in a thicket of brush and boulders near Interstate 287, a shopping center, a local middle school and hundreds of homes — has a history dating to the early 1900s. In those pre-refrigeration days, what is now the Upper Pond was used to produce ice; there was a quarry, since closed, on what is now the Lower Pond.

In 1941, according to a 2008 engineering study, the dam collapsed and was rebuilt on the brook's ledge rocks as a reinforced concrete dam with a fixed timber door. While the door kept the waters of the Blind Brook at bay and flowing gently toward Long Island Sound, it did not prevent high water from spilling over the dam during major storms like Hurricane Agnes in June 1972 and Hurricane Eloise in September 1975. Homes, yards and streets were sometimes badly damaged.

On April 15, 2007, a once-in-a-century nor'easter pummeled the Westchester County seaboard with eight inches of rain in a 24-hour period. Low-lying portions of towns like Mamaroneck and Rye were particularly hard hit[5]. Indian Village, a Rye neighborhood with more than 200 residents where the streets are named for Indian tribes and 3,000- to 5,500-square-foot homes sell for over $1 million, was severely damaged, Mr. Rosenberg said.

The 2008 study[6], by the Charles H. Sells Inc. engineering firm in Briarcliff Manor, showed that Indian Village had filed 113 of the 273 claims for insurance losses in the City of Rye caused by the storm. (The city is a separate municipality from the town of Rye, which includes two villages, Rye Brook and Port Chester.) Officials of Rye Brook and the City of Rye, which owns the dam, decided after conducting flood-mitigation studies to build a sluice gate that could be raised or lowered depending on the volume of water flowing.

Costing $2 million and containing an orifice 15-feet wide by 2.5-feet high, the sluice gate began operation in 2013. Its computer program processes a complicated array of data sent by sensors in the brook that measure, among other things, water levels and temperature, and then adjusts flow rates accordingly. It was that computer program, which Mr. Rosenberg said was accessible through a cellular modem, that had been penetrated. The indictment identified the key Iranian involved in the breach as Hamid Firoozi, 34, employed by two Iranian companies sponsored by the Revolutionary Guards[7].

Mr. Rosenberg said he and other local officials learned of the intrusion in 2013 but were asked not to discuss it.

"They tried to get into it," Mr. Rosenberg said of the hackers, "but they did not activate the sluice gate." Still, he said, "we have to be cognizant of what infrastructure gets hooked up to the Internet."

Correction: March 25, 2016
An earlier version of a picture caption with this article misidentified the street shown in the picture. It is Westchester Avenue in Port Chester, N.Y., not Rye Avenue in Rye.