If you received an invitation to connect on LinkedIn with someone from the Department of Homeland Security, would you be curious enough to check the profile? The correct answer is, of course, no.
While this phishing mail looks superficially OK, the links actually point to an entirely unrelated site on a .de domain. LinkedIn has more than 200 million users, so it's not surprising that it has become the subject of phishing mails.
LinkedIn bombards users with so many emails that ignoring them is often the only sensible strategy anyway. Managing LinkedIn via the site or an app is a safer and simpler option. If you do receive a tempting email, hover over the link to check it before clicking.