Ad-/Tracking-Modules and Privacy Checker

That's not only annoying in many cases, but also a general security risk – as ad- and tracking-modules inherit all permissions from their „host-apps“. Moreover, there are other hidden costs of advertisements: with websites, they at best make up 50% of your traffic, in some cases more than 90%! Not to forget that sometimes there are also malicious ads – something Google Ads isn´t safe from either. So what can be done?

Buy apps. Usually, the paid versions do not contain ad-modules (exception: if the paid version is to be used as an addon to the free one; but unfortunately there are also other exceptions). See also: Apps bezahlen (4/2012)
If there's no paid version (or that contains „sniffers“ as well): think about using an AdBlocker (in most cases, this requires root)
Alternatively, think about using a Firewall or Permission Blocker.
Take your apps exclusively from F-Droid (in my lists they can be identified by the F-Droid Icon). According to a study from 9/2017 this is the only place where neither Adware nor Malware was found (at Google Play they found e.g. ca. 2% Malware)

But first, you've got to identify affected apps:

Identify Ad-Modules

2019-04-20

Exodus Privacy (4.4@239) 2 Github; Video Walk-Through 6/2018
Addons Detector (4.1@8,020) Ǥ 8 $Contains no known trackers \o/$ Vorstellung 4/2012; Intro (Interview) 6/2012
Anti Adware (3.9@19,262) Ǥ 7 Vorstellung 6/2013
AirPush Detector (3.8@42,618) 0 LastUpdate: 2013-07-22 Intro 6/2011; Vorstellung 12/2011
TrustGo Ad Detector (3.7@11,451) 2 LastUpdate: 2015-01-02 Test 4/2012; Vorstellung 11/2012
AppBrain Ad Detector (3.7@9,796) Ǥ 6 Kurzvorstellung 4/2012; Test 4/2012; IzzyOnDroid Recommendation: also lists Social SDKs and developer toolkits; scan engine (database) is still updated even if the app was not
Ad Detector (3.4@2,945) 3 LastUpdate: 2013-07-11
ClassyShark3xodus (0@0) 1 $Contains no known trackers \o/$

Privacy-Checker

2019-04-20

For general privacy-risks, a.o. the following apps watching out:

Camera Blocker - Anti Spyware (4.6@6,384) Ǥ 6 / Camera Block Pro - Anti malware & Anti spyware app (4.5@1,177; ~EUR 7.00) 4 blocks camera access
Privacy Guard (4.5@174) Ǥ 6 LastUpdate: 2017-07-04
Incognito - Spyware Detector and Phone Security (4.4@31,760) Ǥ 10
Cameraless- Anti Spy Camera Blocker Application (4.4@3,642) Ǥ 16 blocks camera access
Exodus Privacy (4.4@239) 2 Github; Video Walk-Through 6/2018
tSpyChecker (4.3@1,453) 0 $Contains no known trackers \o/$ LastUpdate: 2017-03-27
Anti Spy (SpyWare Removal) (4.3@1,391) 2
McAfee App Advisor (4.3@762) Ǥ 22 LastUpdate: 2016-12-31 what does it need those perms for?
Anti Spy for Paranoids (4.3@111) 2
Defenx Privacy Advisor (4.3@6) Ǥ 10 LastUpdate: 2017-07-24
[ROOT] Privacy Assistant (4.3@6) 9 $Contains no known trackers \o/$ LastUpdate: 2017-02-13
PrivacyProxy (4.2@22) Ǥ 10 giving you control of what information is sent out from your device
Anti Spy Mobile Free (4.1@18,724) 0 $Contains no known trackers \o/$ / Anti Spy Mobile PRO (4.3@1,385; ~EUR 5.00) Ǥ 3 Intro 6/2012; AppThread@XDA-Forum
Microphone Block Free -Anti malware & Anti spyware (4.1@2,689) Ǥ 8 / Microphone Block Pro - Anti spyware & Anti malware (4@532; ~EUR 7.00) 5
Privacy Scanner (AntiSpy) Free (4.1@1,327) 0 $Contains no known trackers \o/$ / Privacy Scanner (AntiSpy) Pro (3.7@64; ~EUR 2.50) Ǥ 2 $Contains no known trackers \o/$ Vorstellung 4/2012
Message Spy Remover (Anti Spy) (4.1@736) 5
SpyCamBlocker Free (beta) (4.1@195) 2 $Contains no known trackers \o/$ LastUpdate: 2014-03-14 Disables camera access
Lumen Privacy Monitor (4.1@152) 15
MyPermissions Privacy Cleaner (4@6,130) Ǥ 9 Vorstellung 9/2013 | 11/2013 | 2/2014; 6/2014; Intro 3/2016; alarms you as soon as an app accesses your private data (but not before)
NoSpy MyPhone: Anti Spy (4@588) 11 LastUpdate: 2015-09-29
Anti Spy Detector Free (4@133) 0 $Contains no known trackers \o/$ / Anti Spy Detector Pro (4.4@14; ~EUR 2.00) 0
Androlyzer - Privacy Scanner (3.9@71) 4 $Contains no known trackers \o/$ LastUpdate: 2016-11-05 Detection of malware, spyware, trojans and undesired data leaks; see website
Hidden Apps Detector (3.6@1,280) 2
Clueful Privacy Advisor (3.5@79) 4 LastUpdate: 2017-05-17 Test 4/2012; Vorstellung 5/2013 | 5/2013 | 12/2013; Review 6/2013 | 11/2013; shows potential risks, but excludes its own from the lists

Other Sniffer-Detectors

2019-04-20

Fake Hotspot Detector -AntiSpy (4.5@202) 10
WireTap Detection (Anti Spy) (4.3@4,243) 7
Cell Spy Catcher (Anti Spy) (4.3@2,446) 7 detect Stingray Cell Phone Trackers („IMSI catchers“)
WireTap and Spy Removal (4.3@2,240) 9 Needs your location to detect wiretaps?
Scam Apps Detector (4.3@8) 2 LastUpdate: 2017-05-11
Wi-Fi Privacy Police (4.2@1,208) 5 $Contains no known trackers \o/$ LastUpdate: 2016-10-08 Github; Vorstellung 1/2015 | 2/2015; protects against WiFi tracking
WIFI Privacy (4.2@30) 5 $Contains no known trackers \o/$ LastUpdate: 2016-12-27 protects against WiFi tracking
GSM Spy Finder (4.1@2,912) Ǥ 13 detect Stingray Cell Phone Trackers („IMSI catchers“), but spies itself (see included trackers)
SpyWare Removal (Anti Spy) (4.1@541) 2
[root] Pry-Fi (3.9@6,734) Ǥ 10 $Contains no known trackers \o/$ LastUpdate: 2014-02-17 Vorstellung 2/2014 | 2/2014 | 2/2014 | 2/2014; Intro 2/2014; Test 3/2014; protects against being WiFi-sniffed
SnoopSnitch (3.3@3,275) 15 Intro 1/2015; Video Demo 11/2016; Mike‘s favorite; detect Stingray Cell Phone Trackers
CrappaLinks (0@0) LastUpdate: 2014-10-05 Video Review 4/2014; Kurzvorstellung 10/2014; Github; Remove link masking/tracking from various apps

Further Readings:

Category Ad-Blocker
Category Anti-Virus, Anti-Malware, Anti-Theft
Category App-Locker
Category Permissions
Beware those snooping mods! in the help section
PrivacyGrade: Grading The Privacy Of Smartphone Apps
Das inoffizielle Android Handbuch: Risiken werbefinanzierter Apps / Privacy / Verbindungsdaten
Privacy settings with Google: Google Settings Is a Super Useful Android App You've Probably Ignored
Why „I´ve got nothing to hide“ is wrong: 7 videos a 15 min by DoNotTrack
App-Werbung: Betrug mit verdeckten Videos (3/2019)
Podcast Tracking: Ein Tag im Internet - welche Spuren hinterlasse ich (2/2019)
Thousands of apps are illegally working around the ad ID (2/2019)
Geschwätzige Android-Apps send detailed data to Facebook (12/2018)
Werbe-Apps: Von nervig bis gefährlich (12/2018)
Wenn das Smartphone wissen will, was im Fernsehen läuft (11/2018)
Study: Third Party Tracking in the Mobile Ecosystem (PDF; 10/2018)
90% of the investigated 1M Playstore-Apps set up to transfer information back to Google
Now Apps Can Track You Even After You Uninstall Them / Apps kommunizieren mit Nutzern – auch wenn sie deinstalliert sind (10/2018)
Mobile app data sharing 'out of control' (10/2018)
Apps: Datenschutzerklärung vs. tatsächlich gesammelte Daten (9/2018)
Zu Hülf: Meine App spioniert mich aus! (6/2018)
App-Module (SDKs): So tracken Apps ihre Nutzer (5/2017-11/2018)
App-Module als Sicherheitsrisiko (4/2018)
Study finds over 3,300 Android apps improperly tracking kids (4/2018)
Android: Facebook-Wanze in vielen Apps (4/2018)
Datenlobby kämpft mit Tracking-Brandbrief gegen ePrivacy (3/2018)
Android: Elegante Lösung gegen WLAN-Tracking (3/2018)
LightsOut und Co.: Android-Adware im Google Play Store (1/2018)
Anyone can buy online ads and track your location in real time (10/2017)
App AGB: Diese Vertragsklauseln sind unzulässig (6/2017)
Schnüffel-Module in Apps: Das können Sie tun (5/2017)
Tracking im Internet: Cookies, Cache & Co (3/2017)
So bekommen Sie mehr Privatsphäre bei Android (3/2017)
Datenhändler: Wir sind gläsern – Datensammler (Artikelserie, Start 1/2017)
The Terrifying Cost of »Free« Websites (12/2016) Watch this!
Wie im Internet Geld verdient wird – Markt und Macht der Werbebranche (10/2016)
Warum Datenschutz jeden angeht (und nicht nur diejenigen, die etwas angestellt haben) (7/2016)
Ortsdaten von zwei Apps reichen, um Nutzer zu identifizieren (4/2016)
Tausende Apps scheffeln mit unsichtbarer Werbung Geld (7/2015)
Is Advertising Morally Justifiable? The Importance of Protecting Our Attention (Summary; 7/2015)
Free Apps May Be Tracking Your Phone Without Your Consent (5/2015)
also see: Your free Android apps talk to thousands of ad sites (5/2015)
Mit diesen 7 Tricks schützt Ihr Eure Privatsphäre (4/2015)
Invisible Infrastructures : Online Trackers (3/2015)
The Android Apps That Collect the Most Data on You (12/2014)
Hallo, Datenkrake! – So formt die Werbeindustrie detaillierte Nutzerprofile 1 | 2 | 3 (7/2014)
2013: Zielgruppenspezifische Malware und der Aufstieg (und Niedergang) von Adware (2/2014)
Die Privatsphäre als Produkt: Datenschutz als Geschäftsmodell (2/2014)
Apps sammeln immer aggressiver Nutzerdaten (2/2014; Article smells of BitDefender-Promo; so better "ignore/neutralize" the advertized products)
Studie: Kostenlose Apps verbrauchen bis zu 75 % der Energie für Werbung (3/2012)

2019-04-20

IzzyOnDroid