new york yahoo inc yhoo.o come renew scrutiny federal investigators lawmakers thursday disclose large know data breach history prompt verizon communications inc vz.n demand good term plan purchase yahoo internet business share sunnyvale california-based internet pioneer fell percent announce breach data belong billion users late wednesday follow another large hack report september verizon agree buy yahoo core internet business july 4.8 billion try persuade yahoo amend term acquisition agreement reflect economic damage two hack accord people familiar matter u.s. wireless carrier still expect go deal look major concessions light recent breach accord another person familiar situation ask status deal yahoo spokesperson say confident yahoo value continue work towards integration verizon verizon already say october review deal september breach disclosure late wednesday say would review impact new development reach final conclusions whether proceed company decline comment beyond statement thursday verizon threaten go court get deal repriced cite material adverse effect say people familiar matter ask identify negotiations confidential court delaware yahoo incorporate ever find material adverse effect occur would allow company terminate merger agreement nevertheless threat court case issue successfully use company renegotiate deal experts say concessions yahoo likely give magnitude cyber security breach renegotiate deal price tag would simple also least likely scenario impact data breach apparent time accord erik gordon professor university michigan ross school business likely concession would yahoo agree compensate verizon close deal base liabilities occur two company may also agree extend close deal allow time information come impact breach gordon suggest verizon share rise 0.4 percent close 51.81 line 500 index .spx yahoo close 6.1 percent 38.41 yahoo say late wednesday uncover 2013 cyber attack compromise data billion user account large know breach record say data steal may include name email address telephone number date birth hash passwords case encrypt unencrypted security question answer company add partner affect one partner europe sky plc skyb.l say yahoo provide email service 2.1 million sky.com email account holders unclear many account affect announcement follow yahoo disclosure september separate breach affect 500 million account company say believe launch different hackers white house say thursday u.s. federal bureau investigation probe breach several lawsuits seek class-action status behalf yahoo shareholders file work meanwhile democratic senator mark warner virginia say look yahoo cyber security practice most-recent revelation warrant separate follow-up plan press company cyber defenses weak compromise billion users say statement warner become top democrat senate intelligence committee next year describe hack deeply trouble new york attorney general eric schneiderman urge anyone yahoo account change passwords security question say examine breach circumstances company disclosures law enforcement germany cyber security authority federal office information security bsi advise german consumers consider switch safe alternatives email criticize yahoo fail adopt modern encryption techniques protect users personal data consider repeat case data theft users look closely service want use future security play part decision bsi president arne schoenbohm say statement late breach draw widespread criticism security experts several advise consumers close yahoo account yahoo fall security many ways recommend active yahoo email account either direct yahoo via partner like get rid stu sjouwerman chief executive cyber security firm knowbe4 inc say broadly distribute email yahoo spokesperson response criticism company security measure say thursday commit keep users secure continuously strive stay ahead ever-evolving online threats keep users platforms secure yahoo scrutiny late hack verizon seek new deal term