City Hall’s computer defenses appear to be successful.

The City of Richmond’s computer specialists, it turns out, have dealt with and overcome hacking attempts and other computer challenges that have made headlines elsewhere, officials said.

One example is Ransomware, the vicious software that can take over a computer system and require payment of a ransom to have system information restored.

During the past 12 months, the city has dealt with three or four such incidents, according to Charles G. Todd, interim director of the Department of Information Technology.

“We had city employees with elevated user credentials (administrator privileges) inadvertently introduce malware into the city’s computer,” he stated in an email response to a Free Press query.

“We never contacted the extortionists because DIT staff was able to contain and remove the malicious code and restore server-based files from backups,” he said.

Separately, a few employees “have fallen for phishing scams,” which he described as someone “pretending to be someone else and baiting the victim into revealing sensitive information, such as a user name and password.”

In most of the cases, Mr. Todd said, someone pretended to be from the city’s help desk and gained access by asking the employee to perform a verification task or change some information.

“The phishers were able to use the information to send spam via the victim’s email account,” he said. “DIT quickly detected the issue and took the necessary step to reset credentials” and eliminate the problem.

While hacking has become a government and business headache and was most notorious during last year’s presidential election, City Hall seems to have avoided the problem.

Mr. Todd said he is not aware of any successful incidents of hacking during the last three years in which computer security was breached, allowing unauthorized persons to gain access to sensitive data.

He said the city also has experienced outages that have knocked out computer service to an agency. One case involved the Richmond Sheriff’s Office and another involved the Manchester Courts Building. Service was restored within one to three hours, he said.