text: NHS Digital confirmed so many NHS staff use the search engine that it had started asking them to take a quiz to verify they were "not a robot".
  News site the Register reported one NHS Trust had told staff to "use Bing" instead.
  Google indicated its systems were designed to spot unusual traffic and were working as intended.
  Detecting suspicious traffic from one network can help defeat potential cyber-attacks, such as attempts to try to overwhelm a website.
  The BBC understands Google is not deliberately singling out NHS traffic.
  A Google spokeswoman said: "Our systems are simply checking that searches are being carried out by humans and not by robots in order to keep web users safe. Once a user has filled out the Captcha [security check], they can continue to use Google as normal."
  The NHS is one of the biggest employers in the world, with more than a million members of staff.
  An email sent by an NHS system administrator suggested the number of staff using the search engine was "causing Google to think it is suffering from a cyber-attack".
  NHS Digital told the Register: "We are aware of the current issue concerning NHS IP addresses which occasionally results in users being directed to a simple verification form when accessing Google.
  "We are currently in discussion with Google as to how we can help them to resolve the issue."
  NHS Digital was unable to suggest what NHS staff may be searching for using Google.
target: NHS staff using Google's search engine has triggered one of its cybersecurity defences.