* Stryker experiences global network disruption, no

ransomware detected

* Iran-linked group Handala claims responsibility for

attack, says it is retaliation for strike on Minab school

* Cybersecurity experts warn of increased Iranian cyber

retaliation

* Stryker shares drop 3.6% post-attack, White House says

it is monitoring cyber threats

(Adds context from paragraph two, with expert commentary and a

comment from the White House)

By AJ Vicens and Christy Santhosh

March 11 (Reuters) - An Iranian-linked hacking group on

Wednesday claimed responsibility for a destructive cyberattack

on U.S.-based medical device and services provider Stryker,

according to messages posted to the group's Telegram channel.

The Michigan-based company, with 56,000 employees and

operations in 61 countries, said in a filing with the SEC that

the attack caused disruptions and limitations of access to some

systems, and that the timeline for a full restoration is not yet

known.

Staff and contractors said in social media posts that the

logo of an Iran-linked hacking group has appeared on the

company's login pages. Reuters was not able to verify the posts.

"We have no indication of ransomware or malware and believe

the incident is contained," a company spokesperson said, without

commenting on who may have been behind the attack. Calls to the

company's global headquarters in Portage, Michigan, were

answered with a recording that said the company is "currently

experiencing a building emergency."

Stryker shares ended down 3.6% on Wednesday.

Fears have mounted that Iran, which has sophisticated cyber

espionage capabilities, might retaliate against U.S. or Israeli

entities after the two countries began airstrikes against it.

"This is exactly the type of attack we have been worried

about: Iranian proxies using destructive cyber attacks like data

deletion against U.S. companies to retaliate," said Cynthia

Kaiser, senior vice president of cybersecurity firm Halcyon's

Ransomware Research Center and a former senior FBI cyber

official.

Handala, an Iranian-linked hacking persona that has claimed

multiple attacks on targets in Israel and around the world, said

in a message posted to its Telegram channel that it was

responsible for the attack, which was in response to the strike

on the Minab school in southern Iran "and ongoing cyber

assaults."

The group did not respond to a request for comment sent to

one of its messaging accounts.

The girls' school in Minab was hit on the first day of

U.S.-Israeli attacks on Iran, killing an estimated 150 students,

according to Iran's ambassador to the U.N. in Geneva, Ali

Bahreini. Reuters has not independently verified the figure.

The outages on Stryker's network began shortly after midnight on

Wednesday on the East Coast, the Wall Street Journal reported,

citing people familiar with the matter.

The company's staff found that remote devices running

Microsoft's Windows operating system, including cellphones,

laptops and others configured to connect to Stryker's technology

systems, had been wiped.

A White House official said: "(The) Trump administration is

always proactively monitoring potential cyber threats and

driving a response with our world-class critical infrastructure,

regulator agencies and law enforcement entities."

The FBI and the Department of Homeland Security's

Cybersecurity and Infrastructure Security Agency did not respond

to requests for comment.

Handala has been linked to multiple hack-and-leak operations

as well as disruptive attacks, including cases in which data was

destroyed, Israeli cybersecurity firm Check Point said in a

report Tuesday.

"They are the most notorious group affiliated with the

Iranian regime," Check Point Chief of Staff Gil Messing said in

an email.

Messing added that Check Point has tracked the group for

years and believes they operate under Iran's Ministry of

Intelligence.

"The fact they publicly take responsibility on this attack,

and the fact they know they are linked to the government, show a

new phase in Iran's motivations."