The phrase "Beat the Tigers" is explained this way in a January 21 China Daily article:
Xi Jinping, general secretary of the Central Committee of the Communist Party of China (CPC), vowed to unswervingly fight against corruption and keep power reined within the cage of regulations.This screenshot, taken on January 27, shows that Sina Weibo was censoring searches for the phrase "Beat the Tigers," (打老虎).
During a CPC disciplinary watchdog meeting on Tuesday, as Xi ordered enhanced restraint and supervision on the use of power, he said, "Power should be restricted by the cage of regulations."
. . . .
Xi said the Party should crack down on "tigers" and "flies" at the same time by dealing with illegal activities of officials on the one hand and tackling malpractices and corruption cases, which closely impact the people, on the other.
"No exception will be made when it comes to Party disciplines and law," Xi said. "Cases will be investigated completely and no leniency will be meted out no matter who is involved."
He continued, "Party cadres at various levels should keep in mind that no one can enjoy absolute power outside of the law."
These screenshots show that on January 29 Baidu began censoring search results for "Li Jianguo." Prior to Baidu's censorship, the top search result was a discussion of the Ming Pao report. Following Baidu's censorship the top result was Xinhua's profile of Li.
Baidu's censorship came just hours before Xinhua published a report entitled "Li Jianguo: Earnestly Implement the Spirit of Xi Jinping's Important Charge, Improve the Work Style of the National People's Congress" (李建国：坚决贯彻习近平重要批示精神 改进全国人大会风). That article made no mention of an investigation.
Prior to Baidu's censorship, five of the results on the first page were from January 2013. As this screenshot shows, a day after Baidu imposed censorship the only results from January 2013 on the first page were four links to the same Xinhua article.