The FBI has released its interview notes with Hillary Clinton. Starting on page 30 of the notes (contained in part one of the archive), the FBI describes spearphishing attacks on the Clinton private email system:
Replying to a suspicious email with the question, “Is this really from you? I was worried about opening it!” is a natural human reaction. However, this is not the ideal security response. This report demonstrates how hard it is to tell real emails from well-crafted attacks. SP Guard helps users make these distinctions.