What causes a question to be protected by the Community ♦ user
3541
What is a “protected” or "highly active" question?
5735
Why is the Association Bonus ignored when trying to answer a protected question?
13008
Unable to answer protected question despite having enough reputation
60734
More descriptive "User was removed" explanation
102525
Cannot answer protected question on iOS app
38647
Is there any benefit to allowing code-only answers while blocking code-only questions?
30201
What happens to folks who get question banned, by and large?
72131
Is a StackExchange question only valid if it it's your own problem you're describing? If not, does this still apply in beta?
152818
Can we get a better wording for protected questions?
33204
What should I do if a user posts sensitive information as part of a question or answer?
138266
What questions belong on Super User vs Server Fault?
97906
What can we do to prevent people from posting their coding questions on Meta?
100364
Anomalous community user activity
85087
Answer from a user with 9 on-site reputation but protect option is not available (in sufficiently old question)
124652
Can I prevent others from editing my question?
133102
Is Stack Overflow's content protected?
123468
Protected questions and editing