If two investors get together and trade then its called manipulation.
Visit SEC website to learn more information; http://www.sec.gov.lk/?page_id=426
OFFENCES UNDER THE SEC RULES GAZETTE NO.1215/2 OF 18TH DECEMBER, 2001
In addition to the specific offences set out above, the contravention of any of the provisions of the SEC Act or Rules and Regulations made thereunder shall be an offence as stipulated in Section 51(1)(a) referred to above.
(11) Rule 12: Any person who creates a false or misleading impression of active trading or a false or misleading impression regarding the price of any securities shall be guilty of an offence.
(12) Rule 13: Any person who creates a false market in listed securities shall be guilty of an offence.
(13) Rule 14: Any person who front-runs his client in the manner provided in Rule 14 shall be guilty of an offence.
(14) Rule 16: Any listed company which does not supply with immediate effect any price-sensitive information concerning such company to the stock exchange is guilty of an offence.