A necessary evil
Definition 1 of 1
Pro Tip 1/3Negative Connotation
Implies something is unfavorable but tolerated for a greater good or necessary outcome. 
Though she dislikes dieting, she sees it as a necessary evil to improve her health.
Pro Tip 2/3Colloquial Use
Commonly used in spoken and informal written English, rather than formal or academic texts. 
They see studying grammar as a necessary evil of learning a new language.
Pro Tip 3/3Contextual Understanding
Understanding the specific situation or outcome is crucial when using the phrase to avoid misinterpretation. 
In the context of cybersecurity, constant updates are a necessary evil to prevent breaches.