More than 5 percent of the latest batch of emails from former Secretary of State Hillary Rodham Clinton, released Wednesday, contain classified information — or twice the rate of the previous releases, raising tricky questions about whether the department is finding more secrets or being more thorough in screening the messages.
The emails also show an effort to hack into Mrs. Clinton’s personal account by sending her fake traffic tickets with a Trojan horse file attached. If she had clicked on the file, the hackers could have gained access to her computer.
Five such messages were sent to Mrs. Clinton on Aug. 3, 2011, according to the emails released Wednesday — part of a court-ordered release of more than 30,000 messages Mrs. Clinton shielded from public view until prodded to release them by the State Department, Congress and a federal judge.
Mrs. Clinton has said her decision to use a server she kept at her home did not compromise U.S. national security, but the hack attempts and classified emails suggest there were dangers to her arrangement.
All told, at least 400 messages out of nearly 12,000 emails released so far contain information that the government now deems classified.
But 214 of those messages came in the latest batch of 3,869 messages, for a classification rate of 5.5 percent.
The messages were not marked classified at the time they were sent — usually in 2010 or 2011, for the latest batch — but the government has gone back and determined that they contained information that shouldn’t be public.
The State Department is making monthly releases of the emails as it complies with a court order to release more than 30,000 messages by the end of January.
The messages show the inner workings of Mrs. Clinton’s operation, dealing with high-level diplomacy and more mundane scheduling matters.
One of the latest messages revealed that Cheryl Mills, one of Mrs. Clinton’s closest confidantes, believed hackers tried to get into her private email account — exactly the kind of breach that security specialists fear when federal employees use private accounts to conduct official government business.
“As someone who attempted to be hacked (yes I was one), I am not sure we want to telegraph how much folks do or don’t do off state mail b/c it may encourage others who are out there,” Ms. Mills wrote in a 2011 email exchange involving Mrs. Clinton and her top aides, Huma Abedin, Jacob Sullivan and Anne-Marie Slaughter.
Ms. Slaughter initiated the conversation by saying the State Department’s technology was so antiquated that “even high officials routinely end up using their home email accounts to be able to get their work done quickly and effectively.”
Mrs. Clinton has said she rejected a State.gov account and used an account tied to a server she kept at her New York home because it was more convenient. She has not cited antiquated technology as a reason.
But her decision to host her own account meant that her emails were shielded from public records requests for four years. After prodding by the congressional panel investigating the 2012 Benghazi terrorist attack, the State Department belatedly demanded the messages from Mrs. Clinton and her top aides.
Mrs. Clinton returned more than 30,000 emails in December, but Ms. Abedin and Ms. Mills didn’t turn over all of their records until late this summer. Mrs. Clinton said she discarded some 30,000 other messages she deemed private.
The former first lady and current Democratic presidential candidate said she didn’t break any laws and was allowed to use a private account. She also said the law gives her the power to decide which messages are government business and need to be returned.
A federal judge and a top department transparency official have both said Mrs. Clinton violated policy, but she has insisted what she did was not against the law. On Wednesday, senior adviser Valerie Jarrett said the White House had discouraged Cabinet secretaries from using private accounts.
“Obviously, we want to make sure we preserve all government records, so there was guidance given that government business should be done on government emails and that if you did use a private email it should be turned over,” Ms. Jarrett said.
Ms. Jarrett said the court-ordered release of Mrs. Clinton’s emails shows that the former top Obama diplomat is living up to that guidance.
“She’s working hard to comply to make sure everything is pursuant to the Federal Records Act,” the adviser said.
Republican National Committee Chairman Reince Priebus, though, said the latest batch of emails shows Mrs. Clinton endangered national security.
“Hillary Clinton said at the outset of her email scandal there was no classified material on her secret server, and this release is another reminder she has misled the American people from Day One,” Mr. Priebus said.
None of the emails was marked classified at the time it was sent, but the State Department and five separate intelligence agencies are now combing through all of them and finding secret information in one out of every 20 messages.
In one of the emails sent by Mrs. Clinton, she is involved in the drafting of the U.S. response to presidential elections in Haiti, which were tainted by accusations of corruption that set off violent demonstrations.
The subject line of the email was “Draft Embassy Statement.”
“Did [redacted name] reach you about this?” Mrs. Clinton said in the email to her chief of staff, Cheryl Mills. The email included a string of messages that the State Department deemed classified, citing the code for foreign government information and foreign relations or foreign activities of the United States, potentially including confidential sources.
The State Department redacted the bulk of the statement and the dialogue between U.S. diplomats regarding it.
Thomas C. Adams, whom Mrs. Clinton appointed U.S. special coordinator for Haiti in September 2010, sent the original message that contained a draft of the embassy statement to Dan Restrepo, who at the time served as President Obama’s senior director for Western Hemisphere affairs at the National Security Council.
Mr. Adams marked email “SBU,” the abbreviation for “sensitive but unclassified.” The State Department redacted the text of the draft statement, citing the Freedom of Information Act exemption for material involved in the deliberative process.
The email exchange became classified when Mr. Adams and several of Mrs. Clinton’s top aides, including Mrs. Mills, discussed the “tabulation process” in Haiti.
⦁ This article is based in part on wire service reports.