Still, shares of Yahoo! continued their decline, falling 46 cents, or 1.1%, to $42.34 on Monday afternoon. The stock is down 4% from Sept. 22, the day before Yahoo! announced that a 2014 hack had compromised data from 500 million user accounts. Verizon shares were down 0.7% to $52.19 on Friday.
"It is very, very early stage. We will work with Yahoo! on it and see what the implications are," Amstrong said on CNBC, adding that Verizon learned about the incursion last week.
Armstrong would not comment when asked if Verizon would seek to potentially renegotiate its purchase price for Yahoo!'s core business for $4.8 billion in cash, or $5.9 billion including the purchase of restricted stock units. But he did say that "we really want to be protective of and watch out for" Verizon shareholders, adding that "at the end of the day it's consumer trust that we're focused on."
He also noted that the initial integration of the two companies "is going well."
Despite the size of Yahoo's breach, Robert Peck of SunTrust wrote last week that the deal would not likely trip the "material adverse effect" clause in the Verizon transaction, a customary provision that outlines when a buyer can back out of a deal.